iayicishy
PO Ke
CMR
Hera ds
wad iw
ana wd
yey gd Wen
eet ah ala ealy
trbedbe Wd hee
4
Mt wo
hia
(i aa
a wee
‘alo a wipe
!
f nati
OOK
sora tyaega t
‘
eae Oly ay
‘
? i
PERRO ICN iM 0
USS Maat:
ie ATER
bow
Vel alae gy wad
rata
ey ty yay
HR AeA
yeh
beaded
rid
UR
raha
Pitted bar
(Oe Saran
sn hi AY
,]
TORO MeCN a
Vana. ewkien
OS FAH gw AE Nd
4
‘ Ye
a NG
Ave
Wadley cnt
‘yay
tow
eR?
EAN
a
‘ Mit
Cane eae aD
han Het
Psd et
Gatagio “s,
WC ie)
aid
OUR ay eee a
in tabby hy
be ee
Nw aa ae hs
4 DA
ay
eevee
RD
Waal
‘
ed, OA
uy 4 ote a PC AR
. i ‘ Avie a ne
i ate " POR MN 7
Wea iv ious Lib ir tet
te Brees see
Wi a a aia ta “
td ve i ; ie \
ed AACA eS
My FO ti takai wy
lee 1 sata aan nreliie gale
W 4
AA Ny shutinde
or ye + ¥
i i 3 ki mt “ f ‘ ts a we 4h
iD awe Sain’
AS Wat dN
Meanie
is
ny
ea ‘
4 1"
Naan cturaeas , Seep Aa ait ‘i
ye Moke Ry . law a ’ tht uy pal
if
mR hot ve
ta A aa
Paso ay ney
tbh a Ws) My
hak Gar te
Ft ate aa eos
“ ;
eee
t a tian daa
Hi bi} iy Mi el i Wien uN ” fi WT dae et ae En) a) we
idee Pe
wie bogs Rate WG MICS ihe
oh
i) cid wre mea ic) i eae ‘1
sbWtdn RAD NNW RE
ACheyea 0 uM) ty
Ay AUNT Ar ta MT sab vi aha Ys3 ah ry it
ae ny oF ‘erie ate 9 a Hohl A) UH vo
Va ik Ot dd Vie
4
Peet rm
iat
ve rent
'
Ce
wit ae th ta
i) yste a
le Way
NE abe nee 4
i, ay re oe
aN -
i meant i
berks Nut
i baitath et
bit
i
age\h WG ae
Reentry
Ald Federa iy tie
see itn
ins
ae
+ Ay st \
{tf ‘iy nn "0, f mn 9.
i ‘
SiG
*
“4
aes { i
< Hovis
CAAA alive
Crm
pNjtast) in,
Hae Wave t Can As
ae
yyy
idl ann? eine
SOA ob ih Ro )
es Meek a
ay
rar CRA
Vay
f
De
[ee iF go wed Vea
oe ht aha
fan
My Tata h aa Vie nih
‘y y
Warde Wy Vays
ran | OU) iy
vy aN
fy bait
hits
ee Ce ee
Pe ee
ye
iegit
4 Ha
ae
ates
4 At i Cabal
DURAY v8 anit CA le Bu
Taal as ) stat)
Mas hegs
ues
Mt) Wg he a
Pet aor ean a
dire oa fit
ak eth nt r
Cl cr ey
We ee Me WDD 4
i AUC ee a
Sot Mite
Miri patie:
i vik
hie
ue if
Bytt ite i}
ony a, ‘4h y anbeds {
By Hu " oh
i i
Ry ” eae fy
‘enn
Has
par ei
aes
iM is at
ney tee
Mractl ai
Oe Lies
i) aint
They why
boat ies
Gi Ay hae
‘ COME
bres pf be
oe sie it ( ' BR Ay
; i Pein f ry Ki i 10, mit) rr
i ai . : V0 ‘ ote
f RRNA
hit ae
Me yaleat atid
ip Pe bat
prsie
tt ha As
Aw ‘igs
ra) +
edt
SOURS a
ath Mao
ate
Hes wig?
ti
fits ita 6
aS tas
Att DE An
hin fet
Ra
tf Sp hs h
f Hate
3 ste ie va
ay it Wy ‘
ie
Zaidi
Hoey Kier
Wi
i Walaa se
He Ae
On ry
f eH
WS es
8
$ f
wie Lae nededye ds Frdobe ac
idiots in TOU Lb ae eS
+ eae She Aca
ht
pay gute
Hit ah athe may +
ebb yak
Feige 1H tate
by ite Satine vite f
aie Fe ey oh te s
we iat Miasa ned is
hata eal ga
weit
at
Bint? wns ae Apeitye af
ivi Sit Maay ttt
ety
Hiab
eas
gk
Saigo trSTB YAN
Carre seit)
My cara ‘s yt
Ce
ve
hh te
‘ bib aie
(eur
if
Te
Alt es
68 a Ys Stet f
TTA Phe
ites
edith ED
Tah MED, Ms
stat varia
fa iNew eae
hone we wee
i) HAN A AOA
alse et hw
iia ee ee
Crem ee
bated A Waratah)
whiny
WA
“
4 dei Me aa
She mane ita “is i
we AEE aitagnsetgeanicn “
se et beh AW Mae
‘ UK at wv
oe
¥
in
Tay
a
i
mn
Nana
, Hye Han
i
he
LTR
Pinae
PROCEEDINGS
OF THE
Cambridge Philosophical Society.
VOLUME XY.
Cambridge :
PRINTED BY JOHN CLAY, M.A.
AT THE UNIVERSITY PRESS.
PROCEEDINGS
OF THE
CAMBRIDGE PHILOSOPHICAL
SOCIETY.
VOLUME XV.
OcTOBER 26, 1908—JuNE 6, 1910.
SANA
Cambridae :
AT THE UNIVERSITY PRESS,
AND SOLD BY
DEIGHTON, BELL & CO. AND BOWES & BOWES, CAMBRIDGE.
CAMBRIDGE UNIVERSITY PRESS,
Cc. F. CLAY, MANAGER, FETTER LANE, LONDON, E.C.
1910
CONTENTS.
WOID, 20Nihe
The Laws of Mobility and Diffusion of the Ions for med in Gaseous Media.
By E. M. Wevuisce. (Communicated by Sir J. J. THOMSON)
The Radioactivity of Rubidium. By NoRMAN CAMPBELL
In the Free Pressure in Osmosis. By L. Vegarp. (Communicated by
Sir J. J. THomson.) (Two figs. in Text) .
Therapeutic Inoculation for Generalised Bacterial Infections. By UL.
Noon. (Communicated by Professor G. Smis WoopHEaD.) (Six
figs. in Text) 5 5 : : ;
In the examination of living leucocytes in vitro. By Constant PONDER.
(Communicated by W. E. Dixon.) (Two figs. in Text) .
‘On the Relation between Ionization and Pressure for Rontgen Rays in
different Gases. By J. A. CRowrner. (Communicated by Sir J. J.
Tomson.) (Two figs. in Text) : : :
‘On the Relative Ionization produced by Rintgen Rays in diferent ( Gases.
By J. A. CrowrHer. (Communicated by Sir J. J. THOMSON)
The Relationship between Human and Bovine Tuberculosis. By Professor
G. Smus WooDHEAD . 5 : sian:
The radiation of various spectral lines of neon, helium and sodium im a
magnetic field. By J. E. Purvis
The transmission of Trypanosoma lewisi by fleas and lice. By Professor
G. H. F. Nurran. ieee ct
The presence of anticoagulin in the salivary glands of Argas persicus.
By Professor G. H. F. Nurrauy ! : : :
The mode of action of specific substances. By W. E. Drxon and
P. HaMILi ; : 5
The action of specific substances in toxaemia. By W. E. Drxon and
W. H. Harvey
The Migration Constants of Dilute Solutions of Hy proton uC ee By
C. Currrock. (Two figs. in Text) ; 3
On the Carriers of the Positive Charges of Electr ae said by hot wires.
By Sir J. J. Tomson : : : : .
PAGE
11
13
30
34
38
40
45
53
53
54
54
55
64 .
vill Contents.
An Electric Detector for Electromagnetic Waves. By E. M. WELLISCH.
’(Communicated by Professor Sir J. J. Tomson.) (One fig. in
Text) : : . 3 : : é : 3
Aldabra and neighbouring rade By J. C.F. Fryer: (Plate XID) %
Notes on the larger Cetacea. By D. G. Linus. Cas by
A. E. SHIPLEY) :
Experimental snvestigation as to Decade of the Weight ae a pes on
its state of Electrification. By L. SoutHERNS. (Communicated by
Professor Sir J. J. Thomson.) (Five figs. in Text) ._
Note on an Attempt to Detect a Difference in the Magnetic Properties
of the two kinds of Ions of Oxygen. By Miss D. B. Pearson. (Com-
municated by Professor Sir J. J. THomson) : 3
On the theory of the motion of charged Ions through a Gas. By Professor
Sir J. J. THomson
On the relative velocities of diffusion in aqueous solution of rubidium and
caesium chlorides. By G. R. Minzs. (Two figs. in Text)
Note on the use of the experimental method described in the eis
paper. By A. V. Hitn., (One fig. in Text)
A note on some fossil plants from Newfoundland. By KE. A. NEweLn
ARBER. (Two figs. in Text) : 5 Jacutie : ‘
A note on Cardiocarpon compressum, Will. By Mrs E, A. Neweun
ARBER. (Communicated by E. A. NewELL ARBER)
On a new species of Physostoma from the Lower Carboniferous Rooks ay
Pettycur (Fife). By W. T. Gorpon. (Communicated by E. A.
NEWELL ARBER) : :
On the relation between the fossil ee and the Zygopterideae.
By W. T. Gorpon. (Communicated by E. A. NnweLL ARBER) .
On the occurrence of Schizoneura paradoxa, Schimper and Mougeot, in
the Bunter of Nottingham. By R. D. Vernon. (Communicated
by E. A. NEwELt ARBER)
Notes on the genus Schizoneura, Schimper and Mougeot. By L. J.
Wits. (Communicated by E. A. NewELt ARBER)
On Petrified Plant Remains from the Upper Coal Measures of Bristol.
By D. G. Lintir. (Communicated by E. A. NeweELL ARBER)
On the assimilating tissues of some Coal Measure Plants. =o ET
HamsHaw THOMAS .
The production of Cathode Par Paes ben Homogeneous isc Radic
tions. By R.'T. Bearry. (Communicated by Professor Sir J. J.
THomson.) (Three figs. in Text)
The solution of a system of differential equations occurring in the theory
- of radio-active transformations. By H. Bareman. (One fig. in Text)
PAGE
416
423
a alee
Contents.
1x
PAGE
On double-sixes. By W. BURNSIDE : :
On the Procession and Pupation of the Larva of Cnethocampa pinivora.
By T. G. Epwarps. (Communicated by H. H. BrinpieEy)
Secondary Réntgen Rays from Metallic Salts. By J. L. Guasson. (Com-
municated by Professor Sir J. J. THomson.) (Five figs. in Text)
On the Transmission of B-rays. By J. A. CRowrHeEr. (Six figs. in Text)
Some Experiments on Ionisation in Dried Air. By S. G. Luspy. (Com-
municated by Professor Sir J. J. THomson) - Nj th Pte cagstrrs
On the Scattering of rapidly moving paren Particles. - By Professor
Sir J. J. THomson : :
Jacobi’s double-residue theorem in eae to the Hebry of point-groups.
By A. C. Dixon : ‘ : ; : :
On the phosphorescence observed on the glass of vacuum tubes when the
pressure is not very low. By Professor Sir J. J. THomson :
On the Mobilities of the Ions produced in Air by Ultra- Violet Light. By
A. Lt. Hugues. (Communicated i Professor Sir J. J. THomson.)
(Four figs. in Text) . : ‘ : 5 : : : :
On a Dissymmetry in the Emission of the Cathode Particles which are
produced by Homogeneous Rintgen Radiations. By R. T. Buarry.
(Communicated by Professor Sir J. J. Taomson.) (One fig. in Text)
On Right- and Left-Handedness in eae By R. H. Compton. (One
fig. in Text) :
On Accident in Heredity, with sbhota ee to Rich and ye
Handedness. By F. J. M. Srrarron and R. H. Compron .
Discontinuities in Light Emission. Il. By- Norman CAMPBELL .
The Absorption of Bromine by Lime. By W. A. R. Wriixs. (Com-
municated by Dr Frenron) 5 : ‘ ; : 4 :
Note on the Reduction of Bae Chloride. fa H. O. Jonxs oe
J. K. Marruews
The development of Trypanosoma lewisi in the Rat Flea secmiopimine
fasciatus). By C. Srrickuanpd and Dr N. H. SwWELLENGREBEL.
(Communicated by Professor NUTTALL) . ‘
The Development of Gnomonia erythrostoma, the Cause of Cherry ee
Scorch Disease. By F. T. Brooxs.
The Absence of Living Tubercle Bacilli from some Otel Fete
Lesions in Man. By Dr Louis Copserr
Note on the Radiwm-content of the Waters of the Cam, Wie ae Tap
Water and some Varieties of Charcoal. By JoHN SATTERLY. ee
municated by Professor Sir J. J. THomson) ; ;
The Resolution of Externally Compensated Bases into their Optically i]
active components. By Professor PopE and J. Reap .
428
431
437
449
459
465
472
482
483
ddl
534
536
540
545
x Contents.
The Resolution of Be opapaverine. By Professor Porr and C. S.
GIBSON : : ; - : é : :
Further study of the Products of Chlor imation of a-Picoline. By Dr SELL
Formation of wie acid derivatives. By Dr Fenton and W. A. R. WILKS
The fate of uric acid in the dog. By HaroLp ACKRoyD. a
by Mr W. E. Dixon) : ‘ :
The Adsorption of Acids by Carbohydrates. By F F. Ropryson. (Com-
municated by Dr FrntToN) : : : :
The results of Sterilisution Experiments on the Cambri Water. By
G. Stas WoopHEAD 5 : :
Preliminary note on the properties of sos ee bed ae Radiation.
By R. Wuippineron. (Communicated by Professor Sir J. J.
THomson.) (One fig. in Text)
Further notes on the procession of Cnethocampa ROE: a Jats lel.
BRINDLEY. (Plates XIII, XIV) : :
Proceedings at the Meetings held during the Session 1909—1910 .
Index to Vol. XV.
PLATES.
Puates I—III. To illustrate Mr Purvis’ paper .
Pirates IV—IX. To illustrate Mr Orange’s paper
Puate X. To illustrate Mr Gregory’s paper
Puate XJ. To illustrate Mr Purvis’ paper .
Puate XII. To illustrate Mr Fryer’s paper
Puates XIII, XIV. To illustrate Mr Brindley’s paper
PAGE
545
546
547
o47
548
85
217
239
247
340
576
PROCEEDINGS
OF THE |
CAMBRIDGE. PHILOSOPHICAL
| SOCIETY.
VOL RVs PART &
[MicwartMas TERM 1908.] eos
Cambridge :
AT THE UNIVERSITY PRESS,
Sine AND SOLD BY
DEIGHTON, BELL & CO. AND BOWES & BOWES, CAMBRIDGE.
CAMBRIDGE UNIVERSITY PRESS WAREHOUSE,
C, F. CLAY, MANAGER, FETTER LANE, LONDON, E.C.
1909 -
Price Two shillings and sixpence.
23 February, 1909,
Valle reer reeecr dns
NOTICES.
1. Applications for complete sets of the first Seventeen
Volumes (in Parts) of the Transactions should be made to the —
Secretaries of the Society. :
2. Separate copies of certain parts of Vélames L—XI. of the
Lransactions may be had on application to Messrs BowEs & ©
Bowes or Messrs Deicuton, BELL & Co., Cambridge.
3. Other volumes of the Transactions may be obtained at
the following prices: Vol. xu. £1. 10s..6d.; Vol. x1. £1. 2s. 6d. ;
Vol. xiv. £1. 17s. 6d.; Vol. xv. £1. 12s. 6d.; Vol. xvi. £1. 10s. Od. ;
Vol. xvi. £1. 2s. 6d.; Vol. xvitl. £1. 1s. Od.; Vol. xrx. £1. 5s. Od. ;
Vol. xx. £1. 10s. Od. ; Vol: xx1. No. 1, 3/-; No. 2, 4/-; Nos. 3 ee
4,1/6; Nos. 5 ad 6. 3/-.
4. Complete sets of the Proceedings, Volumes I.—XIV.,
may also be obtained on application to the Secretaries of the
Society.
5. Letters and Communications for the Society should be
addressed to one of the Secretaries, he
Mr A. E. SHIPLey, Christ’s College. [Biologieal.]
Dr E. W. Barnes, Trinity College. [Mathematical.]
Mr A. Woop, Emmanuel College. [Physical.]
6. Presents ae the Library of the Society should be ad-
dressed to
The Pee Troy
New Museums,
Cambridge.
7. Authors of papers are informed that the Illustrations and
Diagrams are executed as far as possible by photographic “process”
work, so drawings should be on a large scale and on smooth white
Bristol board in Indian ink.
8. Members of the Society are requested to inform the
Secretaries of any change of address.
PROCEEDINGS
OF THE
Cambridge Philosophical Society.
The Laws of Mobility and Diffusion of the Ions formed in
Gaseous Media. By E. M. Wettiscu, Emmanuel College.
[Communicated by Sir J. J. Thomson.]
[Read 9 November 1908. |
The information we possess with regard to the size and
structure of the ions formed in gases by the action of Réntgen
rays is almost entirely derived from a knowledge of their rates
of diffusion and their velocities under given electric forces*. In
order to obtain this information theoretical expressions are
necessary for the coefficient of diffusion (D) of an ion through
a gas and for its velocity (&) under unit electric intensity. From
considerations based on the kinetic theory of gases Langevin+
has shown that & and D are expressible in the forms:
eL LV
ee MY fe 3°
where e denotes the charge associated with the ion, M the mass
of the ion, Z its mean free path through the gas, and V its mean
velocity of thermal agitation. From these forms however no
very exact information can be deduced inasmuch as the values
of the quantities involved cannot be directly determined from
experiment. In the present paper expressions are given for
k and D which involve only known physical constants of the gas
and from which, therefore, we may expect to derive reliable
information with regard to the constitution of the ion.
A molecule is regarded for the present purpose as a nucleus
surrounded by a “sphere of force” of radius 4s.
* J. J. Thomson, Conduction of Electricity through Gases, 2nd edit. Art. 38.
+ Ann. de Chim. et de Phys. v1. 28, p. 324, 1903.
VOL. XV. PT. I. 1
2 Mr Wellisch, The Laws of Mobility and Diffusion
An ion is regarded as involving two distinct elements:
(i) a mass (independent of the charge). Considering this
element alone, let us represent the ion as a nucleus surrounded
by a sphere of force of radius $3’.
(ii) a charge e (electrostatic units). During motion of the
ion through the gas the effect of this charge is (as will be shown)
to increase the radius of the force sphere of the ion without
altering the mass.
A collision occurs between any two molecules when the distance
between their centres is equal to the sum of the radu of their
force spheres.
As the ion moves through the gas the charge associated with
it attracts the neutral molecules; there results an increase in the
mean collision frequency of the ion and consequently a diminution
in its mean free path.
Expression for the ionic mean free path.
Consider the motion of an ion and a molecule regarded in the
light of two interacting free particles. Let & denote the potential
due to the polarisation of the molecule by the charge on the ion*,
so that the force, taken as wholly radial, between the ion and the
molecule is given by dT tt a distance r. Let us reduce the
molecule to rest and consider the relative motion as the ion
approaches it so that the velocity at infinity was U. The
interacting forces must now be considered as being derived from
eee
a potential ae
R, m denoting the mass of the molecule.
The shortest distance r to which the ion and the molecule
approach is given by the equations:
bU =ru,
M+m
$M (w — U*)= Te,
where w denotes the velocity of the ion in this position and
b is the length of the perpendicular from the molecule to the
rectilineal path of the ion.
We deduce
R =i
Pin ee
2M+m g
702 ier
_ * The polarisation of the molecule by the electric field is regarded as negligible
in comparison with that due to the ionic charge.
of the Ions formed in Gaseous Media. 3
A collision will take place if
D) | Re
b <0? {1+ Tim i
2M+m
where o=4s'+4s, the sum of the radii of the force spheres
of the ion and molecule.
If R=0, ie. if the polarisation of the molecule due to the
ionic charge is negligible, the condition for a collision reduces
to b<o, as is otherwise obvious.
The connection between the velocity U and the mean thermal
ionic velocity V can be deduced by the application of Maxwell’s
law of distribution of velocities. We obtain
U2 =)? (142).
m
1 Mn
1 Mm 2 1 Al 2»
Hence Oa =4MV?=mw"; thus na
mean kinetic energy of the molecular motion.
The effect of the polarisation due to the ionic charge is
therefore, as far as collisions are concerned, to replace o® by
2
o ! + st
mv?
U? is the
Now the mean free path of an uncharged body of the same mass
: Sadat M)\>
and dimensions as the ion is given by frnota/ il ss = , where
n denotes the number of molecules per c.c. Hence the actual
mean free path of the ion is Z where
T= an Wi! + cal + a.
: m mv
Expression for the potential R due to the polarisation of the
molecule by the tome charge.
If the molecules of a gas are polarised by an electric field
of intensity X, the electric moment per c.. is ae where
K denotes the dielectric constant of the gas.
The electric moment () of a molecule is therefore om
The force on the molecule is p - which is equal to
K-11 dx?
San ° dr ~
The potential is therefore given by
4, Mr Wellisch, The Laws of Mobility and Diffusion
when the molecule is polarised by the field due to the ionic charge.
This expression for R assumes that the polarising field is
uniform throughout the volume of the molecule. Langevin* has
obtained the general expression for R in the case of a spherical
molecule and finds it to be given by a series of which the above
is the most important term.
Expressions for the mobility and coefficient of diffusion of the
aon. .
Let » denote the coefficient of viscosity of the gas, p its
density, p the pressure in dynes per sq. cm. and / the molecular
mean free path. Let 7, p,, p,, A, denote the values of n, p, p, K
respectively corresponding to a temperature of 0° C. and a pressure
of 760 mm. of mercury.
The charge e carried by the ion is taken as equal to the
charge (#) on the monovalent ion in the electrolysis of solutions.
This equality was established from measurements of the mobility
and rate of diffusion of gaseous ions}. The exact value of the
ionic charge is not required in the present treatment inasmuch
as e only enters in the expression n,e = n,#, which has been shown
from experiments in electrolysis to have the value 1:30 x 10”,
E being measured in electrostatic units. The product n,# is
denoted by A.
The gas is supposed throughout to be at a temperature of 0° C.
We have the following equations:
eL LV
CV Oe
n = tnmvl
= aN 2ns?
M 2h
=i! ea Sere > ee lee ho ib
L taana/ 1+ {i+ at, where go =4s +45
K-11 2
oe San | o!
MV? = mv” (equipartition of energy)
gs
* loc. cit. p. 317.
+ For the evidence in support of this equality the reader is referred to J. J.
Thomson, Conduction of Electricity through Gases, 2nd edit. Art. 39.
of the Ions formed in Gaseous M: edia. 5
ni=A
PS mm
p= spr.
We deduce
1 i |
An, 5 (m\? M\? ae A(K-1)e 7
=s5 0 8 (or (1 + =) (1 ate {1 Teen aie
When the mass and dimensions of the ion are the same as
those of a molecule we have M =m, s’ =s, and the expression for
the mobility becomes
( ae 2) —1
pip Anrnmv" s*
This expression can be transformed into
Gea
PP 2px'P1
In a similar manner we obtain for the case when M=™m, as
path, Hadad
p ( 21 Pi
Consider the expressions (a) and (8) which have been found
for the mobility and coefficient of diffusion through a gas of an
ion regarded as a molecule carrying a charge equal to that
associated with the monovalent ion in electrolysis.
For a given medium Kj, p; and p, are constant; whence
i varies inversely as p provided y is constant. Now by Maxwell’s
law* the coefficient of viscosity of a gas is independent of its
density ; consequently over the range of pressures for which this
law holds good we should expect the ionic mobility to vary
inversely as the pressure, a conclusion which has been verified
by experiment. Similarly we should expect the coefficient of
diffusion to vary inversely as the density over the same range.
The expressions for & and D involve only known physical
constants of the gas and are therefore directly comparable with
the results of experimental observation. The results obtained
by substituting the observed experimental values of the quantities
involved are given in Table I. The values of the viscosity
coefficients and of the dielectric constants have been taken from
Landolt and Béornstein’s Tables (8rd edition); the constant p,
was taken as 1,013,610 (dynes per sq. cm.).
The seventh column in the table affords an indication of the
effect on the mobility of the electric polarisation of the molecules
by the ionic charge; it will be seen that the effect is quite
* Vide Jeans, Dynamical Theory of Gases, p. 252.
Mr Wellasch, The Laws of Mobility and Diffusion
6
‘on[vA uBeyy 4.
“TOYTIM aT} Aq
apem ATyUe0er “poystiqud yok you ‘syueutrtodxe Jo s}{nsex oyy ov sonyBa AqrTIqotH paadasqo oyy ‘me pue %O ‘eq ‘*Ey Jo uOdeoxe oY} TTIW »
0g: 66: 06: 96: 91-§ OCF SG 989 | 8-SST "TOO | SPMOTYowszqe9 wogzreD
Og: 8G: PG: 68: DUNG GFL 69 oss | LPL o"H’O | “ aeyje AUQG
0g: GE: II. 8-1 90-21 FGI 66 886 | &P9 1O°HO | * eprropyo [Aug a
9G: GE: 61: GL-T 918 OF6 8 G0G 7 OH) 4 "> " poyoore [Ayam
91 OL: IZ OF-G GI-¥G OLL 96 91 hit "HN |" foe eTUOULCLW
98: 6L- Ts: 10-¢ 08% LOT jaa 961 tT O'N |" eptxo snoaqtyy
13: Lt 18: 10-€ GG 96 Gal 961 ad “00 (| 1" SprXorp uoqrey)
08:1 9GT Go [LG 9G-¢ #¢ 161 er GE Oped Sg * weskxoQ
49.1 1e-1 8G-G FEE 6¢ E91 Gol 8G °N secon estes UesOA,INT
OL G0: 1 91-1 8G-G GLE 69 691 GCI 8G OO | Sprxouout woqaey
C6-L 01-9 ZE-9 8&-0F 6-4 9% G8 6 b “fs uesoapézy
18-1 98-1 GET 18-G OL-¢€ 6G DM 661 ae peo aan: Coe pase LAE
‘oes/utd | ‘oas/"uId | *oes/*tH9
poarosqg Sears 00g Td.'de 1 1 aero
Wh =) ; Telia e0LX (t-'y) | oor x4 cOT x bd repnoojopy | PIAUMIOT Iodva 10 sex
II Or 6 8 L 9 G 14 te G T
‘[ ATA,
of the Ions formed in Gaseous Media. 7
considerable. Column 8 gives the values of the mobilities under
a potential gradient of 1 volt per cm. which would be possessed
by a molecule carrying a charge # if there were no retarding
effect due to this polarisation. The remaining columns give the
values of the mobilities as deduced from expression («) together
with the observed experimental values of the positive and negative
ionic mobilities; these values correspond to a real or hypothetical
pressure of 760 mm. of mercury.
Unfortunately the values of K have been determined experi-
mentally for only a very limited number of gases and vapours;
in consequence there do not appear in the table several vapours
whose mobilities have been ascertained.
Considering that we are comparing the observed values of the
mobility with absolute values calculated from various physical
constants of the substances the agreement is in several cases
quite satisfactory; however, in the case of ammonia and the
vapours, there is a marked divergence between the calculated
and observed values, the former values being invariably smaller.
The values of the dielectric constants for the vapours appear to be
inordinately large, and, in this connection, it is teresting to note
that it is also in the case of vapours that there is a marked
departure from Maxwell’s law, K =n?, where n is the refractive
index. The following table will serve as an illustration:
TABLE II,
Gas K kK? 2
H, 1:000264 1:000132 1:000138
CO 1:000690 1:000345 1:000340
CoO, 1:000960 1:000480 1:000450
N,O 1:001070 1:000535 1:000500
Air 1:000590 1:000295 1:000294
NH, 1:0077 1:0038 1:000370
C,H,Cl 1-0155 1-0077 1-0010
C.H,0 1-0094 1-0047 1-00086
In the case of Maxwell’s law the reason for the departures
is probably the existence in the molecule of free periods with
durations long compared with that of the incident wave period*.
It is possible that, m the case under consideration, owing to free
periods of long duration in the molecules of the vapours, these
* Vide Drude, Theory of Optics, Eng. trans. p. 389.
8 Mr Wellisch, The Laws of Mobility and Diffusion
have not time to be completely polarised by the adjacent ionic
charge during a collision. It is worthy of mention that the
large values of K which have been experimentally obtained for
ammonia and vapours have been ascribed by some authorities
as being partially due to traces of conductivity which they possess.
Without dwelling further on the cause of these departures
from the mobility law, it appears that, on the whole, the experi-
mental values of the mobilities of the ions can be explained
approximately on the supposition that the ion consists of a single
molecule of the gas, with which is associated a charge equal to
that carried by the monovalent ion in electrolysis. It has been
shown from considerations based on the kinetic theory of gases
that, irrespective of any theory as to the structure of the ion, the
ascertained mobility values lead of necessity to the conclusion that
the volume of the ion is in all cases greater than that of the
corresponding gaseous molecule. The question arises: what is
the nature of this volume? On the one hand, if we neglect the
influence of the charge on the mean free path of the ion, we are
led to the conception of the ion as a cluster of molecules held
together by forces arising from the polarisation due to the electric
charge. On the other hand, the effect of the charge on the
collision frequency has been shown to be equivalent to an increase
in the molecular sphere of force such that the resultant effective
volume is sufficient to explain approximately the observed
mobilities. On this view the effect of the charge is to cause
the ion itself and the neighbouring molecules to deviate from
their rectilineal free paths; Sutherland*, by assuming such
deviations to occur in the case of gaseous molecules by reason
of attractive forces between them, was able to explain accurately
the observed variation of the viscosity of gases with temperature.
Langevin} has obtained an expression for the ionic mobility by
using the dynamical method employed by Maxwell in the kinetic
theory of gases; he concluded that the experimental values of the
mobilities lead to the necessity of regarding the ion as a cluster
of molecules. The question as to the nature of the volume of the
ion as determined from the experimental mobility values could be
decided if the ratios < for the different gaseous ions were known.
In this connection it is worthy of mention that Professor Sir J. J.
Thomsont has recently measured this ratio for the positive ions
formed by cathode particles in oxygen at low pressures and came
to the conclusion that the ion consisted of a single charged oxygen
molecule.
* Phil. Mag. v. 36, p. 507, 1893.
+ Ann. de Chim. et de Phys. vit. 5, p. 270, 1905.
+ Phil. Mag. v. 16, p. 680, 1908.
of the Lons formed in Gaseous. Media. 9
In the course of recent experiments made by the writer to
ascertain the ionic mobilities in a series of gases and vapours
it was found that the mobility (&) varied inversely as the pressure
(p) over a wide range of pressures; however, there was observed
a tendency of the product pk to increase at low pressures in the
case of air, nitrous oxide and carbon dioxide, and a tendency for
it to diminish in the case of vapours, e.g. ethyl chloride, when the
pressures approached the vapour pressure at the temperature under
consideration. Such deviations from the law pk = constant could
be ascribed to variations in the size of the cluster constituting the
ion; however, they follow readily from the expression (a) of the
mobility if we take into account the deviations from the law of
Maxwell which states that the coefficient of viscosity of a gas or
vapour is independent of its density. In the case of gases it is
known that 7 tends to diminish as the pressure is reduced beyond
a certain value*; such a diminution would, according to the theory
here given, tend to increase the value pk. In the case of vapours
it has been established that 7 increases rapidly as the saturated
state is approached ; in fact, as a result of Warburg and von Babo’s
experiments on the viscosity of carbon dioxide at high pressures,
Meyer+ came to the conclusion that the experimental values above
certain pressures could be explained only by supposing carbon
dioxide to behave as a liquid, the density of which is practically
independent of pressure; an increase in the value of 7 would,
according to expression (a), diminish the product pk, a result in
accordance with experimental observation.
In conclusion, it is of interest to note that, on the supposition
given above as to the nature of the ion, a satisfactory agreement
can be obtained between the calculated and observed values of the
coefficients of diffusion of the gaseous ions. The values of these
coefficients have been determined by Townsend} for four gases.
Instead of using the ascertained expression (8) which is really
involved implicitly in the expression («) of the mobility, a slightly
different procedure is advisable.
If D denote the coefficient of diffusion of the ion through the
gas, and d that of a molecule through the gas, we then have from
the preceding theory
ID db ib: (K, — 1) 7 A279?
TaD Heo 2p ps
The nature of the agreement between the calculated and
observed values is shown in the following table:
* Vide Jeans, Dynamical Theory of Gases, p. 253.
+ Kinetic Theory of Gases, Eng. trans. Art. 90.
+ Phil. Trans. A. 193, p. 129, 1900.
10 Mr Wellisch, The Laws of Mobility and Diffusion of the Ions.
TABLE ITI.
.< |(Ky- 1rd?) ge ;
Gas 2p,7, observed
+:
Caleulated = Observed q
Air 3°70 SiO) ‘032 028 043
Jake 5:39 1:31 “205 “235 -190
O, 3°56 189 ‘041 025 ‘040
CO, wage ‘109 ‘031 023 026
* Calculated from Loschmidt’s observations.
Vide Jeans, loc. cit., p. 274.
i
Mr Norman Campbell, The Radioactivity of Rubidium. 11
The Radioactivity of Rubidium. By NorMAN CAMPBELL, M.A.,
Trinity College.
[Read 9 November 1908. ]
1. In the first paper by Mr Wood and myself* on the radio-
activity of the alkali elements, it was stated that rubidium as well
as potassium was found to be radioactive, and that the rays from
the former metal were less penetrating than those from the latter.
Owing to the difference in the penetrating powers of the rays, the
relative activity of the two elements can not be determined directly
by a comparison of the total ionisation caused by the rays from
a thick layer, but it can be determined by measurements of the
activity of layers of varying thickness. Such measurements on
potassium sulphate were described in a recent paper}: similar
measurements have now been made upon rubidium sulphate.
2. The experiments were made in a manner exactly similar
to those on the potassium salt, and the same apparatus was used.
The sample of rubidium sulphate used was specially prepared by
Kahlbaum: its purity was tested by precipitation by barium
chloride: the weight of the sulphate precipitated agreed within
the limits of error (1 °/,) with that predicted from the accepted
atomic weight of Rb. Some difficulty was experienced in obtaining
layers of the requisite thinness and uniformity: the method
adopted ultimately consisted in scattering the finely powdered
salt over the surface out of a vessel of the nature of a pepper-pot.
The following table gives the results obtained:
| alt in tr aie Mass of salt in tra Ate
| EM enc) ay Activity enn y Activity
6:20 A473 29°31 87°3
10°69 65:2 41°66 90-0
13°44 67-4 43°95 90:5
16°56 Con 52:76 93°3
16°81 ot 63:06 94:7
22°58 (5)
These experimental points lie less closely on a theoretical ex-
ponential curve than the corresponding points for the potassium
salt: the rubidium rays are probably less homogeneous.
* Proc. Camb. Phil. Soc. x1v. 1, pp. 15—21. + Ibid, xtv. 6, pp. 557—567.
12. Mr Norman Campbell, The Radioactinity of Rubidium.
3. The method of calculation explamed on pp. 563, 565 of
the last paper give directly J,, the activity of an infinitely thick
layer of the area (oc) of the tray, and the product me , where J is
o
the absorption coefficient of the material for the rays it emits,
and p the density of the material. If a is the ionising power of
the total radiation from 1 gramme of the material, when all that
radiation is absorbed in air, then
For rubidium metal we obtain
a = 14-47 + 0365, o= 53:2 421.
For potassium metal, using the figures given in the last paper, we
obtain
a= 2003 + -0376, *= 8-23 + 0-1.
It appears then that, though, for layers infinitely thick and
containing the same proportion of the active metal, the activity
is shghtly greater for potassium than for rubidium, the intrinsic
activity of the latter metal is at least seven times as great as that
of the former.
It will be noted that the statement that the penetrating
power of the rubidium rays is considerably less than that of the
potassium rays is confirmed. The difference is so notable that it
may be discovered readily by covering the active layer with a sheet
of stout paper. Such paper absorbs half of the rubidium rays, but
not more than 5°/, of the potassium rays. It is clear, therefore,
that the activities of the two elements cannot be attributed to a
common constituent.
Prof. McLennan and Mr Kennedy* have stated that they have
been unable to detect any activity in rubidium salts. But, since
they have revised some of their statements concerning the activity
of the alkali metals, it is not impossible that agreement will be
obtained in this matter also.
* Phil. Mag. Sept. 1908, p. 377.
Mr Vegard, On the Free Pressure in Osmosis. 13
On the Free Pressure in Osmosis. By L. VEGARD, Cand.
real. (Research Student at the Cavendish Laboratory). [Com-
municated by Sir J. J. Thomson. |
[Read 9 November 1908. ]
1. In the introduction to their paper on osmotic pressure*
Berkeley and Hartley mention that a method for studying osmotic
phenomena is given by the determination of what they call the
osmotic force, and this method “depends on the determination of
the rate at which the solvent will flow through a semipermeable
membrane into a large quantity of solution when there is no
pressure on the latter. A knowledge of this rate together with
the frictional resistance will enable the osmotic force to be
calculated in absolute units.”
The authors, however, do not enter further into the question,
and we get from this no clear idea as to the strict definition of the
osmotic force. ;
The following paper contains some experiments done in this
direction as well as some conclusions to be drawn from the
experiments. The experiments consist in some determinations
of the frictional resistance and: of velocities produced by osmosis
when solution and solvent are exposed to the same pressure. The
cell used is the same as used in the experiments upon osmosis
described in an earlier papert.
Determination of the Frictional Resistance.
2. The frictional resistance depends on the velocity and is
measured by the pressure that must be applied in order to press
the solvent through the membrane with the velocity under con-
sideration. If pressure and velocity are denoted by Q and V
respectively we have Q=f(V) provided temperature is kept con-
stant. To find this function we have simply to determine the
velocity corresponding to different pressures.
The measurements were made with the same osmometer as
described in an earlier paper and the way of proceeding the same
as used for the determination of osmotic velocities only that now
the solution was replaced by the pure solvent. The relation
between Q and V has been determined in two sets of measure-
* The Earl of Berkeley and EK. G. J. Hartley, Phil. Trans. Roy. Soc. 1906,
p. 481.
+ L. Vegard, Phil. Mag. Vol. xvi. No. 92, 93, 1908.
14 Mr Vegard, On the Free Pressure in Osmosis.
ments corresponding to a considerable difference in the maximum
electric resistance of the membrane. Before each experiment the
cell was electrolysed after which it was placed for about thirty
hours in distilled water in order to remove possible substances
soluble in water. The measurements gave the following result:
TABLE I.
Experiment 1. Experiment 2.
Date: Middle of May. Date: June 8.
Electr. Resist. 350,000 ohms at 2° C. Hlectr. Resist. 130,000 ohms at 7° C.
Temp. 15°C. | Temp. 15°8° C.
Q V Q V
3°21 atm. 39 mm./hour | 4°33 atm. 78 mm./hour
(OAs 155 Rs | SO ss 155 -
COEF pee 300 - eee ler 270 Pe
264 580 5 I agai 231 Oe Ne 420
|
Determinations of Osmotic Velocities.
3. The velocities were measured with the osmometer earlier
described for some aqueous solutions of cane sugar and no pressure
was applied on the solution. The measurements including also
the determination of the frictional resistance in Exp. 2 were
carried out as quickly as possible in succession and in the order
of increasing concentrations. The membrane was not electrolysed
between each trial. Thus it was secured that the properties of
the membrane were kept as nearly as possible the same under the
whole series of measurements. The results are given in the
following table.
The temperature was kept at 15°C. which very nearly was
the temperature of the room.
The velocity is here given in an arbitrary unit as the number
of mm. which the water level in the capillary from the cell*
changes in one hour. For the sake of comparison with other
experiments we shall find how this unit is connected to the
absolute unit. To find this we must know the area of the -
membrane (Q) and the inner diameter (d) of the capillary. For
the apparatus used in Cambridge O= 17-0 cm? (very nearly) and
* See description of apparatus, loc. cit. p. 248.
Mr Vegard, On the Free Pressure in Osmosis.
15
TABLE II.
3 § & g 2 ¢ Time for observation of velocities a z28 g ga
gee | B83 saws (Sos
S) zs, aa =a o-n =|
1a.) eel June 9, 3.23 p.m.—4.23 p.m. 3.53 p.m. | 155
: ¥ Ae seit Galli ss yells) Bee 152
June 10, 11.10 a.m.—11.28 a.m. | 11.19 am. | 366
be 11.35 ,, —11.45 ,, A Oe 336
a lea aia Lila. 11.48 ,, 320
300 | 28:0 5 11.51 ,, —12.3l p.m. | 12.11 pm.| 286
B 12.31 p.m.—12.55_,, 12543) 55; 268
e LEO) epee Sn. 1 OGOk. 252
“i eS ye Gin See ep 244
June 10, 3.23 p.m.—3.46 p.m. |. 3.35pm. | 402
= eb R SAG ie AN is | 4.00 ,, 354
eS Nee Mein en te eat oe eel 886
. DAO a5 et) OS) nae eae ae 328
June 1], 10:22 a.m.—10/28 am. | 10:25 am. | 770
+3 10.28 ., —10.34 ,, HO ee. 700
“ HORS = — OSA OTe IND s30o 660
i ese tees lel onan TD ee Ee 506
600 | 85-6 a S353) 54 ——1 22.10 pam ee oa 2, 468
a 12.16 p.m.—12.50 ,, 12.33 p.m.| 458
= 12.55 ,, — 2.01 ,, 8S oe. 421
a4 205: i — 3-080 55 QBs Pas 398
fs S12. Ay eee Bhd are 378
d=0-060cm., then if the velocity in absolute and relative units
is denoted by V’ and V respectively, we find
461.10°V = V’ [em. sec.];
V’ can either be considered as the number of cm.’ passing each
em.? in one second or as the average linear velocity of the fluid
close to the membrane.
16 Mr Vegard, On the Free Pressure in Osmosis.
Discussion of the Eaperiments.
4, The relation between the friction pressure and the velocity
is represented in Fig. 1 B curve II, corresponding to Exp. 2, Table I.
We see that as far as the observations go the points are distributed
round a straight line. Consequently we have
where A is a constant characteristic of the membrane and the
fluid, and dependent on the temperature. We shall call it the
Specific Resistance of the system.
The law for the motion through the membrane is the same as
that for the motion of a viscous fluid through narrow tubes. This
fact is simplest explained by assuming that the liquid also during
the passage through the membrane maintains the character of a
liquid. Then in points inside the tubes of the membrane the
fluid should possess a certain hydrostatic pressure and the cause
of the motion at each point should be found in the pressure
gradient at the point.
The values of the specific resistance corresponding to the two
experiments are—using the method of least squares—found
to be
Exp. 1. A =0-0463 or A’=1:02. 10% [dyn. cm. sec].
iRixqos 250 ea — 00492 s0nAy — 10302 3
A corresponds to the units given in the table, A’ to absolute
units.
We see that we get nearly the same value for the specific
resistance in the two cases and that in spite of the fact that the
maximum electric resistance in the last experiment was not half
of that in the first one, where the frictional resistance even is
somewhat smaller. Thus the maximum electric resistance seems
to give a very delicate test for the permeability of the membrane.
When the membrane first is well formed the mechanical resistance
against the water flow will be very little altered for very con-
siderable changes in the maximum electric resistance.
5. In Fig. 1 A the measurements given in Table II are
represented by curves giving the velocity as a function of time
reckoned from the time when the solution was brought into
contact with the membrane. This time was not exactly observed
so there may be a fault of a few minutes in the time of beginning.
We see that the velocity begins with a rather large value, but
falls very rapidly until at a certain value the curve makes a very
sudden bend. In the case of the three lowest concentrations the
curve assumes a horizontal direction showing that the osmosis
has reached a steady state. In the case of the highest concen-
Mr Vegard, On the Free Pressure in Osmosis. 17
tration, however, the velocity after the sudden bend of the curve
continues to fall.
The condition for a steady state and the time taken for
reaching it depend on several circumstances. A nearer study
of this question would require a special research. I shall here
only call attention to some circumstances which seem to have an
effect.
yeloce Ty
60 Qtr.
C12)
Presseere
Fig. 1.
The time depends to some extent on the dryness of the mem-
brane at the moment when the solution is brought into contact
with it. Thus the membrane in the second experiment, Table II,
was dried with filter paper while in the third the membrane was
just so wet as to give a regular reflection of light. The result
was that the steady state occurred much sooner in the third
experiment and that in spite of the fact that the concentration
was greater.
The steady state sets in more suddenly and is better marked
for dilute solutions than for more concentrated. We shall later
come back to this question. Further the steady state is better
marked and more suddenly obtained when the membrane is more
perfect. So eg. in the measurements described in the earlier
paper, where the maximum resistance was much greater, the
stationary state in all cases was reached within half-an-hour. For
VOL. XV. PT. I. 2
18 Mr Vegard, On the Free Pressure in Osmosis.
the sake of comparison the curve for experiment II* is put upon
Fig. 1 A as a dotted line.
The power of giving a well-marked steady state after this first
sudden bend of the curve is a quality that does not belong to any
membrane showing osmotic activity. Even for the system here
under consideration it appears to be a matter of degree just as _
the power of giving a reversion pressure near to the osmotic
pressure is a power only possessed by the very best membranes.
It will surely be of great interest to see how the different systems
behave in this respect.
6. When the steady state is well defined the velocity correspond-
ing to this state can be considered as a function of concentration,
temperature, and further of some quantities dependent on the
membrane and the fluid. Instead of concentration we can
introduce the osmotic pressure 7. As long as the properties of
the membrane and the temperature can be considered as con-
stants we are led to consider the variation of the velocity A, with
the osmotic pressure of the solution. The relation between 7,
and A, is represented in Fig. 2B, curve I. On the same figure is
also drawn the curve giving the relation between the velocity and |
the friction pressure (curve IT).
We see that curves I and II stand in a very characteristic
relation to each other. The friction line is a tangent to the curve
at the zero point.
A line parallel to the 7 axis cuts the curves in two points
(7 A.) and (QA,) which we shall call corresponding points, then
Q is the pressure necessary to force the pure solvent through the
membrane with a velocity equal to the osmotic velocity A, called
forth by a solution of osmotic pressure 7. In general we have
for corresponding points @ <1, and = will decrease for increasing
7 7
velocities; but when the velocity decreases towards zero we get
Lim (2) Srid:bken hah ee (2).
Ay=0 \To
Let Q, 7, A» be values belonging to corresponding points.
for different values of A,
If we calculate the quantity Wiis
OY)
we find that it gives a constant value. Remembering that Q= AA,
we get the following simple equation for the curve
An)
* L. Vegard, loc, cit. p. 404.
Mr Vegard, On the Free Pressure in Osmosis. 19
The curve is determined by two parameters A and A». Of
these it is only the first one for which we have a physical inter-
pretation. As regards 2,, we see from the equation that when A,
approaches X,, 7) approaches infinity. Thus A», 1s the upper limit
for the osmotic velocity in the stationary state. As to its physical
interpretation it will depend on A, further it must depend
on the coefficient of diffusion for cane sugar in water ; for it is
evident as the velocity is to be produced by the action of the
solution the velocity must be so small that the solution is able to
maintain a certain concentration in the layer next to the mem-
brane.
Some values of X,,, calculated for a series of velocities from the
curve directly observed are given in the following table.
ne ee
100 mm./hour 470 mm./hour
200 7" 430 a
300 ‘ 463 09
350 Ee 480 %9
Mean value 461 mm./hour = 2:13. 10-§[cm. sec.—"].
7. From the very intimate relation between the friction line
and the velocity curve we can draw some important conclusions as
regards the mechanism of osmotic flow.
The work (a) required in unit time for pressing the water
through the membrane with a velocity A, is
a= KQNo,
where « is a constant dependent on the units. In the case of
osmosis we must be able to assume that in order to bring the
water through with a velocity }, an amount of energy (a’) is
required which cannot be less than the energy required for
pressing pure water through with the same ene Then we
must have
a’ S da. :
But on the other hand the maximum of energy EL which the
system can deliver in unit time is equal to the osmotic pressure
multiplied with the volume of solvent, which enters into the
solution in unit time, or
EE = xo.
Now the work (a’) necessary to call forth the motion of solvent
through the membrane cannot be greater than /, consequently
KT Ay Sa S KQr.
2—2
20 Mr Vegard, On the Free Pressure in Osmosis.
This relation holds for all velocities. Letting ’, converge towards
zero we get
1 Lim (“| stim (2).
Ay=0 \KIT Ao Ay=0 \T
Regarding equation (2)
: a’
he = .
or ima @ Kar Ny KOA) 0 — Ee eee (4).
do=0
Thus we see that for small velocities the whole energy of the
system is made available for the motion through the membrane and
the work (a’) required for the motion under osmosis is just the same
as the work (a) required for pressing the pure solvent through with
a velocity equal to the osmotic velocity.
As the work is the same we must assume that also in the case
of osmosis we have a motion of pure water through by far the
greatest part of the membrane. But the motion of pure water
must have its cause in the fall of hydrostatic pressure in the
direction of the motion just sufficient to counteract the friction
corresponding to the osmotic velocity.
8. From this we are led to consider the variation of hydro-
static pressure through the membrane. In those cases where
there is a layer next to the solvent where there is only pure
solvent we shall in this layer have a fall of pressure in the
direction of the motion, and when the pressure on the solution is
less than the corrected reversion pressure (7 )* we find that if we
pass through the membrane from the side of the solvent the
hydrostatic pressure will first fall to a minimum value and then
increase to the pressure of the solution. In the latter part the
motion takes place against the pressure fall and cannot be a
motion of the fluid in bulk, but is an intra-molecular motion
maintained by the energy made available when the two liquids
are brought into contact.
The difference between the pressure on the solvent and the
minimum pressure we shall call the free presswre of osmosis.
The general features for the variation of hydrostatic pressure
through the membrane is indicated in Fig. 2. AF, AF, ete.
represent the free pressure.
If the distance from the minimum point to the surface next to
the solution is n/, where J is the average thickness of the mem-
brane, then an approximate value for the free pressure q is given
by the equation
qg=(n—1) Ad.
* See L. Vegard, loc. cit. p. 264.
Mr Vegard, On the Free Pressure in Osmosis. 21
The pressure gradient is 2) and if we knew 7 this could be
A :
found ; but at all events we see that as far as 7 can be considered
constant \ would give a relative measure for the pressure gradient
near the solvent surface. In the case where n is a very small
quantity we get
G.— AN — Pe riChion Manessuke ss ener ese ee” (5).
")
A
y
@)
Y
q
X
SS
A-f-—-—--—-—---y
Solu lion Membrane Solvent
Fig. 2.
In the case of our system we have seen that for small velocities
n is very small and the free pressure 1s determined by equation (5).
Regarding equation (2) we further see that for small velocities the
Sree pressure is equal to the osmotic pressure.
9. In order to explain the properties shown by the osmotic
velocity we are led to assume that also in the case of higher
concentrations the quantity n will be very small in all those cases
22 Mr Vegard, On the Free Pressure in Osmosis.
where the stationary state is well marked. We shall here mention
some reasons that strongly support this view.
(1) The velocities for higher concentrations are connected to
those for lower with a very simple function, which naturally must
support the assumption of a similar mechanism.
(2) The form of the curve in the case when the stationary
state is not obtained shows clearly that the first sudden diminution
of the velocity has a cause independent of that which causes
the diminution after the sudden bend. The first diminution is
naturally explained by the fact that the concentration next to the
membrane is diminished on account of the flow of solvent, the
latter is naturally explained by assuming that the solution on
account of the high free pressure and of want of semipermeability
is gradually forced into the membrane; for then the path along
which the motion takes place as a diffusion will be augmented
and the velocity diminished. From this point of view it seems to
be a necessary condition for the forming of a well marked steady
state that n maintain a small value.
(3) Another support for our assumption we get by comparing
the velocities here found with the velocities corresponding to
a =0 given in the earlier paper*. In spite of the great difference
in the maximum electric resistance of the membrane all the
velocities very nearly give the same curve. On the other hand
we saw that the frictional resistance kept very nearly constant
from one experiment to another. Now the value of n, however
great or small it is, must depend on the degree of semipermeability
or upon the maximum electric resistance. If then n had a con-
siderable value, we should expect that the velocity in the stationary
state should vary greatly with the electric resistance, this pone
not the case we must assume x to be a small quantity.
10. As long as m is a small quantity the free pressure is
determined by equation (5) and we get the following rule:
Let (qr) and (a Xo) be corresponding points, then g is the Free
Pressure developed in the stationary state of osmosis with a solution
of Osmotic Pressure 1».
The highest free pressure in the steady state will be AX»,
which in the case considered is only 23°3 atmospheres.
When n is small in the steady state it must be the more so
before this state is reached and even when the stationary state is
not well defined we must be able to assume that n is very small
at least at the moment the velocity sets in. In the case of the
highest concentration the free pressure at the beginning of osmosis
has a value of about 40 atmospheres.
As the free pressure cannot be greater than the osmotic
pressure the possible velocities must lie between ~ and = where
* loc. cit., Exp. I, II, III. .
Mr Vegard, On the Free Pressure in Osmosis. 23
qm, 18 the osmotic pressure and q the corresponding free pressure in
the steady state. From equation (38) follows Lim — 1) =.
Ao=0 0
This gives an explanation to the fact that the osmosis for small
concentrations immediately assumes a velocity very near to that of
the steady state.
11. When the pressure on the solution is augmented, the
properties are no longer so simple as they are when 7 =0. The
degree of semipermeability begins to play a more important part
as regards the velocity. As stated in the earlier paper the
absolute value of the velocity for pressures less than the reversion
pressure and when other circumstances are the same is greater
for a more perfect membrane. The increase of pressure was
accompanied by a sudden decrease in the velocity, and this
decrease is the greater the less perfect the membrane is. If the
membrane was quite stable for pressures and quite semipermeable
we should expect that an increase of the pressure on the solution
with an amount 7 would have the same effect on the velocity as
if the concentration was diminished to a value C corresponding to
an osmotic pressure 77)— 7. As a consequence of this the velocity
curve in the interval 0 < 7 <7, would be
Ax
eco 2
Xm
where A and 2X, should have the same values as before if we
assume the qualities of the membrane and the temperature to be
the same. The direction of the tangent at the reversion point —
should be that of the friction ine. In general we find at this point
dar
dx
point we find
ty ih = —
>A, only if the characteristic point lies near to the reversion
dar
dn
ease of the more general rule that the direction of the velocity
curve* just before reaching the characteristic point at least for
more perfect membranes is very near to that of the friction line
corresponding to the same membrane and temperature.
12. From the preceding considerations we see that the experi-
ments are very well explained by the assumption of a hydrostatic
pressure inside the membrane which leads to the theory of the
Free Pressure. This theory, however, gives no explanation of the
manner in which the semipermeability is brought about in the
layer next to the solution. The effect of the membrane is
equivalent to a very great resistance against the flow of solution
in bulk whatever .may be the manner in which this resistance is
brought about.
nearly equal to A. This seems to be a special
* See L. Vegard, loc. cit., Exp. I, I, III.
24 Mr Noon, Therapeutic Inoculation for
Therapeutic Inoculation for Generalised Bacterial Infections.
By L. Noon, B.C., F.R.C.S. John Lucas Walker Student of
Pathology in the University of Cambridge. [Communicated by
Professor Woodhead. |
[Read 23 November 1908. ]
It will be conceded that recovery from a generalised bacterial
infection depends on the defence-mechanism of the patient being
called into action. To an invasion of bacteria Nature replies with
a reaction which has for its object the increase of the natural
defences. Since, however, this reaction often fails, it is the
business of the medical man to ask whether Art may not improve
on Nature in this respect. If the natural reaction is delayed or
incomplete, that is, if it is not the best, the most efficient reaction
of which the patient is capable, we had better seek to improve
matters by the use of an appropriate stimulus.
The following experiments are directed to shew that the
presence of large numbers of infecting organisms throughout the
system is not generally a sufficient stimulus to set the protective
mechanism of the tissues into action at once; while on the other
hand a subcutaneous injection of a suitable dose of the killed*
bacteria provides a generally efficient stimulus.
The organism used was the B. pseudotuberculosis rodentium.
When this was injected into the peritoneal cavity of a rabbit or
guinea-pig there followed a general peritonitis, associated with the
formation of miliary abscesses in the liver and spleen, and in
guinea-pigs also in the lungs. The abdominal lymphatic glands,
as also frequently the mediastinal glands, become caseous. At
death the blood was found to give a pure culture of the organism
in every case. ‘The bacillus is nearly related to that of plague
(B. pestis). The disease is nearly always fatal in guinea-pigs ; of
rabbits, which received an infecting dose of 3, of a 24 hours’ agar
slope culture, nearly one half died.
The disease is therefore a severe one, and widely spread in the
body of the experimental animal. The natural defensive reaction
against this disease consists first of an increase of opsonine.
Later on an agglutinin appears, but no bactericidal or antitoxic
substances can be demonstrated satisfactorily.
I traced the evolution of opsonic resistance in rabbits which
had been infected as described above, and I found at once that a
period of inertia follows on the infection. During this period the
* The killed organisms referred to in this paper were subjected to a temperature
of 60° C. for half an hour.
Generalised Bacterial Infections. 25
disease progresses while the defensive mechanism makes no
answering effort. There is no considerable rise in the opsonic
index of the blood for the first five days of the disease (Fig. 2).
This phenomenon was observed in nine rabbits, none gave a con-
trary result. Three of the rabbits died at the end of this critical
period. In those which survived, the opsonic index usually rose
rapidly, and recovery set in. In guinea-pigs a similar period of
inertia was observed, most of the animals died about the fifth
day, a few lived longer and shewed a rise in the opsonic index, but
only one recovered.
Fig. 1 gives the opsonic histories of a batch of ten guinea-
pigs, which were all infected with similar doses on the same day,
and which have been arranged in three groups according to the
length of time during which they survived an infection. It is
seen that the three guinea-pigs which lived longest had shewn
high indices previous to their infection, and also shewed a capa-
bility to produce a relatively large increase in opsonine in response
to the disease. The animals which died earlier were those with a
past history of medium or low indices. Their indices remained
low during the disease.
From the above it is clear that the natural reaction to the disease
is delayed so late, that many rabbits and most guinea-pigs may be
said to die without a struggle. An injection of killed bacilli
beneath the skin of a normal rabbit is followed by a very different
sequence of events (Fig. 2). In this case the animal responds to
the stimulus with a prompt increase of opsonine, which reaches
about double the initial value within 48 hours. The same result
was obtained with five rabbits which were given various doses
between 5000 million and 80,000 million killed bacilli per kilo-
gramme of body weight. A smaller dose evoked a doubtful
response or none at all. A similar contrast between the diseased
and inoculated rabbits, also appeared with regard to the formation
of agglutinin (Fig. 3). Five rabbits which were inoculated with
killed bacilli, all had strongly agglutinating sera on the fifth day.
Three diseased rabbits, which were tested, produced agglutinating
sera first on the ninth day, and even then the observed agglutinating
power was relatively small.
It cannot be held that, in disease, the protective mechanism
is held in check by an inhibitory influence. If a normal rabbit
responds readily to a subcutaneous inoculation, a diseased rabbit
responds still more readily to such a stimulus, as is shewn on
Fig. 4. After a dose of 250 million dead bacilli per kilogramme
of body weight on the fourteenth day of the disease, the opsonic
index of rabbit 10 rose from 1°5 to 2°5 within 24 hours. In dealing
with diseased animals, however, the dose of vaccine must be care-
fully regulated. An excessive dose produces an irregular reaction
(Figs. 5 and 6).
26 Mr Noon, Therapeutic Inoculation for
Conclusion.
The presence of a generalised bacterial infection is not an
efficient stimulus to call forth the best protective reaction of which
an experimental animal is capable.
DESCRIPTION OF FIGURES.
Fig. 1. Curve I, mean of opsonic indices of three guinea-pigs
which survived infection more than 12 days (one recovered).
Curve II, mean of indices of six guinea-pigs which survived from
6 to 10 days.
Curve III, index of guinea-pig which survived 5 days.
(a) Date on which all the guinea-pigs were infected with equal
small doses of B. pseudotuberculosis, intraperitoneally.
(6) One guinea-pig died.
(c) Four died.
(ad) Two died.
The first dot of each curve represents two separate estimations of
the index of each guinea-pig.
Fig. 2. Continuous line, composite curve of opsonic indices of
nine rabbits which were infected with living bacilli on day 1.
(a) Three of these animals died.
Interrupted line, composite curve of indices of five rabbits, inocula-
ted with killed bacilli on day 1.
Fig. 3. Agglutinating power of rabbits of Fig. 2.
Continuous line, diseased rabbits (three animals).
Interrupted line, inoculated animals.
The numbers at the bottom refer to the same days as those in
Fig. 2.
Fig. 4. Opsonic index of rabbit which received a subcutaneous
dose of 250 million killed bacilli per kilogramme of body weight on the
14th day of the disease (a).
The dots represent independent estimations, the curve is drawn
through the mean of each pair of estimations.
Fig. 5. Opsonic index of a diseased rabbit which received a sub-
cutaneous dose of 5000 million killed bacilli per kilogramme of body
weight. Pairs of independent estimations.
Fig. 6. Opsonic index of the rabbit of Fig. 5, after receiving a
subcutaneous dose of 500 million killed bacilli per kilogramme of body
weight (a). Pairs of independent estimations.
Generalised Bacterial Infections. 27
28 Mr Noon, Therapeutic Inoculation for
AQ? {| U077v129n756Y
Fig. 3. Fig. 4.
Generalised Bacterial Infections.
§
|
E
Ss
¢
r
ose
e
o-—_
° ww i)
oa) >] et
29
Nornal
30 Mr Ponder, On the examination of
On the examination of living leucocytes in vitro. By CONSTANT
PonpDER, M.A., Emmanuel College. [Communicated by
Mr W. E. Dixon.]
[Read 23 November 1908.]
The satisfactory examination of living leucocytes has presented
many technical difficulties. Methods have been mainly employed
whereby the movements, and escape of the leucocytes from blood
vessels, have been observed in the tissues of a living animal, or
the leucocytes have been obtained, in the fluid from serous
cavities, abscesses, or blisters, and studied in suspension, in a
“hanging drop.” It is possible to obtain a fairly clean pre-
paration by centrifugalizing citrated blood, as in Wright’s opsonic
method, and by the usual laboratory process, in which a thin film
of blood, prevented from drying, is examined on a warm stage;
a few white cells can be found, but their appearance is much
masked by the presence of the red cells.
The method which I am going to describe gives a perfectly
clean preparation of a great quantity of leucocytes obtained direct
from any blood; the leucocytes can be kept alive for some time, in
order that their movements and other physical properties can be
studied, while the manipulations are so simple that they may be
carried out by a class of students. I believe, moreover, that the
method may be useful in research work on these most important
cells, for it is also possible in this process to allow leucocytes free
movement for some hours, in relation to extraneous substances
introduced in their midst, in other words to study their chemiotaxis
“in vitro,” or again, one can actually watch their behaviour, when
moving amongst a suspension of bacteria. One can also suggest
the interest of observing the behaviour of pathological cells, such
as those obtained from the blood of a patient suffering from one
of the severe anaemias.
The method. The necessary apparatus is to be found in all
pathological and physiological laboratories, the only unusual
material needed is modelling clay or “ Plasticine,’ which can be
obtained anywhere.
The essential point is the preparation of a blood-chamber,
whereby the white cells are allowed to escape from the clot and
adhere to the surface of a slide, or coverslip, the clot being
afterwards removed.
To make this chamber a morsel of plasticine, half the size of
a pea, is rolled out until it is as thin as the lead of a pencil and
about an inch and a half long; this is then taken and gently
living leucocytes in wtro. 31
fixed on a clean slide, so as to wall in a small chamber, with an
entrance passage leading into it, thus: ;
Plasteine
A drop of blood is allowed to fall into the chamber at 4,
a coverslip is superimposed and gently pressed down with a glass
slide, so that as the plasticine is flattened, blood and air are driven
out of the passage B, which must be kept patent, so that the
chamber is completely filled with an even layer of blood, thus:
SN
This needs a little practice to perform successfully, but under
the usual circumstances, a small air bubble in the chamber does
no harm.
The chamber is now incubated, at about blood temperature,
for any length of time, from ten minutes to three or four hours,
according to requirements.
For a class of students a very simple arrangement, doing away
with the need for an incubator, is as follows. A warm stage is
prepared under a microscope, by means of a copper strip, one
end of which, resting on the microscope stage, is kept at blood
temperature (the melting point of a fragment of cocoa butter can
be used as a rough indicator), when the other end is heated by a
very small flame; on the end above the flame, a flat white dish,
filled with normal (‘75 °/,) saline solution, is placed, at a point on
the copper (easily found by experiment) where the saline solution
also keeps warm at a temperature of 38°C., or a little below.
The whole slide, on which the chamber has been prepared, is
immersed in the dish of saline, at blood temperature, and so
incubated for at least ten minutes.
During the period of incubation the blood clots and the
leucocytes escape and adhere firmly in hundreds to the surface
32 Mr Ponder, On the examination of
of the slide and coverslip, which form the glass floor and roof of
the blood-chamber; it is now only necessary to clean away the
clot. To do this, the coverslip is removed while under the surface
of the warm saline solution by passing beneath it the point of a
knife or needle, and what remains of the clot and plasticine is
scraped away from the slide with a small knife. The slide should
now be well washed in the warm saline until all free red cells
have been rinsed off; this is shown to have taken place completely
by the disappearance of any reddish colour, and on holding up the
slide to the light a grey film can be seen, which consists entirely
of leucocytes, adhering to the surface of the slide.
If now only a temporary preparation is needed, it is merely
necessary to take the slide out of the warm saline bath, super-
impose a coverslip, taking care that plenty of saline lies beneath
it, and examine it on the warm stage under the microscope. If,
however, the preparation is to be kept some time, or it is desired
to bring in contact with the leucocytes some other fluid such as
serum, containing a suspension of bacteria, it is necessary to
construct on a coverslip, a plasticine chamber, similar to the one
originally described for obtaining the leucocytes—though in this
case with walls made as thin as possible—and having carefully
filled this with a large drop of the saline, or fluid, with which it is
desired to bring the leucocytes in contact, to press the slide down
on it, so that the chamber is completely filled with the fluid, and
the leucocytes on the surface of the glass become situated on its
floor.
As an alternative preparation, the coverslip of the original
blood-chamber which is also covered with leucocytes, may be
taken, cleaned as described above, and pressed down similarly on
a chamber (made this time on a slide) which contains a drop of
saline or the fluid with which it is desired that the leucocytes
shall come in contact; the leucocytes in this case are on the
under surface of the coverslip, so that the preparation resembles
that of a “hanging drop.”
The actions of the leucocytes can by this method be studied in
two ways. Firstly, they may be allowed to live and move in the
primary blood-chamber for some hours, the preparation being kept
in an incubator (evaporation does not take place, as the blood dries
across the narrow entrance and seals it), and then, when it has
been cleaned, fixed, and stained, the positions the leucocytes have
taken up, with regard to any foreign substance, can be observed.
Secondly, if the primary preparation is only incubated for ten
minutes, and the leucocytes are then transferred to a second
chamber, we have a means whereby their movements and inter-
actions with foreign substances can take place while under
observation.
living leucocytes in vitro. 33
Throughout this process the question of temperature is of some
importance; it is advisable that the slide to which the leucocytes
are adherent should be kept at a temperature not much below that
_ of the blood, otherwise the cells become circular and are liable to
be washed off; on the other hand, if the preparation is heated much
over 40° C., the leucocytes become disintegrated and disappear.
I have found that the leucocytes will continue their movements
for about three or four hours in the primary chamber, or for about
an hour in the secondary; this is probably to be explained by the
fact that the CO, tension becomes so high as to terminate their
existence sooner when the red blood cells have been removed.
VOL. XV. PT. I.
34 Mr Crowther, On the Relation between Ionization and
On the Relation between Ionization and Pressure for Rontgen
Rays in different Gases. By J. A. CrowTuer, B.A., St John’s
College. [Communicated by Sir J. J. Thomson.]
[Read 23 November 1908.]
1. In the absence of any secondary radiation, the amount of
ionization per cubic centimetre produced in a given gas by the
passage of Rontgen rays of given type and intensity should be
proportional to the mass of the gas present per cubic cm. ; that is,
if the temperature is constant, to the pressure of the gas. Thus
in the absence of any secondary radiation, the ionization-pressure
curve should be a straight line passing through the origin.
If, however, the action of the rays on the gas generates
secondary rays, this will no longer be the case.
It was shewn in a previous paper* that in the cases of air and
carbon dioxide, the energy of the penetrating secondary radiation
is simply proportional to the pressure of the gas, and this result
has subsequently been confirmed for the more powerful radiators.
Since this type of radiation is sufficiently penetrating to pass
through the whole of the gas between the electrodes in the
apparatus employed, the ionization produced by it will be pro-
portional to the intensity of the secondary radiation and to the
pressure of the gas; that is, to the square of the pressure of the
gas. The ionization-pressure curve should thus have the form
I= Ap+ Bp’,
where J is the ionization and p the pressure. For most gases
at the pressures employed in the present experiments the
energy of this secondary radiation is too small to make any
appreciable alteration in the shape of the curve. Taking Barkla’s
value (00024 times the primary) for the energy of secondary
radiation from a cubic cm. of air as beng approximately correct,
it can be shewn that in the case of the most efficient radiator
used, namely ethyl bromide, the energy of secondary radiation at
a pressure of 160 mm. of mercury is only about 3 °/, of that of the
primary beam; or since the secondary radiation is in this case
about three times as absorbable as the primary, the secondary
ionization should be about 9 °/, of that produced by the primary
rays at the pressure named. Since ethyl bromide gives off more
than five times as much secondary radiation as methyl] iodide, and
two hundred times as much as air, it is evident that the ionization
produced by the penetrating secondary rays in these gases is
negligible.
* Crowther, Phil. Mag. x1v. Nov. 1907, p. 653.
Pressure for Rontgen Rays in different Gases. 35
It should, however, be quite perceptible in the ionization
pressure curve for ethyl bromide, and on turning to Fig. 1 it will
be seen that this is the case.
The curve for ethyl bromide, unlike those obtained for other
gases, has a distinct upward tendency, and from the magnitude of
its departure from the tangent through the origin, it is easy to
deduce that, at a pressure of 160 mm., the ionization due to the
secondary rays is about 16 °/, of that due to the primary.
For the other gases tried the curves shew that the effect of
the penetrating secondary rays may be neglected.
lonisation
* The curve for air is not on the same scale as the others.
100 150
Pressure mm.
Fig. 1.
2. It was thought possible that in addition to the penetrating
secondary rays there might be some soft secondary radiation
(possibly soft @-rays) emitted by the gas under the action of the
Rontgen rays. It was with the special object of investigating
this point that the present experiments were undertaken. It can
easily be seen that if the pressure of the gas is so low that the
soft secondary rays from the gas are not completely absorbed in
3—2
36 Mr Crowther, On the Relation between Ionization and
the gas before reaching the walls of the ionization chamber, the
lonization-pressure curve as before should have the form
I[=Ap+ Bp’.
When, however, the pressure is high enough to cause the
complete absorption in the gas of the soft secondary rays from
the gas, the ionization produced by these secondary rays will be
simply proportional to their energy, that is, simply proportional to
the pressure of the gas; and the whole ionization in the gas will
again follow a simple pressure law.
Jonica tion
“Pressure mm
Fig. 2,
The apparatus employed consisted of a gas-tight brass box
with an aluminium window to admit the rays; the ionization was
measured between a pair of parallel plates placed inside the box
but outside the direct line of action of the primary beam, which
was limited and defined by perforated lead screens.
A second aluminium window at the far side of the box allowed
the primary rays to pass out of the box, so that the amount of
Pressure for Réntgen Rays in different Gases. 37
absorption undergone by them could be measured. This was
necessary in order to correct the results obtained, for the absorp-
tion of the primary rays before reaching the electrodes, which in
order to avoid secondary rays from the aluminium window were
placed some considerable distance within the box. This correction
(which varies with the pressure) has been applied to all the results
given in this paper. A second similar chamber was filled with air,
and used as a standard.
3. The first experiments were made with the plates 6 cms.
apart. These failed to give any indication of any departure from
the simple pressure law (except, as stated above, in the case of ethyl
bromide at the higher pressures). It was thought that this might
be due to the distance between the plates being sufficient to
absorb completely any soft secondary rays emitted by the gas,
even at the lowest pressures employed. The apparatus was then
altered so that the distance between the plates was only 5 mm.;
the aperture of the primary beam being suitably reduced by
means of lead slits to a width of about 2mm., and the experiment
repeated.
The results obtained connecting pressure and ionization are
given in Figures 1 and 2, Fig. 1 giving the results for com-
paratively high pressures (up to 200 mm.) and Fig. 2 the results
for ethyl bromide and methyl iodide at pressures below 20 mm. of
mercury. The upward trend of the ethyl bromide curve is evident
from Fig. 1. Apart from this all the curves are sensibly straight
lines passing through the origin. There is thus no evidence of
any appreciable amount of soft secondary radiation from the gas
itself. If gases do emit these soft secondary rays they are either
too absorbable to pass through 24 mm. of gas (the half distance
between the electrodes) even at the lowest pressures employed, or
else they are too small in amount, compared with the ionization
produced by the direct action of the primary rays, to be appreciable.
The former hypothesis is not probable. By allowing the
primary rays to graze one of the aluminium electrodes it was
shewn that the soft secondary rays emitted by the aluminium
under the action of the Réntgen rays passed through the whole
distance between the plates without being completely absorbed
by ethyl bromide at a pressure of 20 mm. of mercury. It seems
probable therefore that practically the whole of the ionization is
produced by the direct action of the primary rays.
388 Mr Crowther, On the Relative Ionization produced by
On the Relative Ionization produced by Réntgen Rays in
different Gases. By J. A. CrowTHEr, B.A., St John’s College.
[Communicated by Sir J. J. Thomson.]
[Read 23 November 1908.]
It may be of interest to place on record the following results
which have been obtained during the course of a series of experi-
ments, still in progress, on the passage of Réntgen rays through
gases. The apparatus was that described in a previous paper*.
A beam of Réntgen rays was fired through the gas, between two
parallel plate electrodes, care being taken to avoid any portion of
the beam falling upon either of the electrodes. If this precaution
is neglected very different values are obtained owing to the large
amount of soft secondary @ radiation given off by the electrodes
under the action of the primary rays.
The measurements given under the column headed “soft
rays” were made with the softest rays which would produce any
appreciable amount of ionization, and the aluminium window was
made very thin (about ;4;mm.) in order to cut off as little as
possible of the soft radiation. The measurements labelled “hard
rays” were made with the bulb as hard as it was possible to work
it with a Rudge induction coil worked by a turbine mercury
interrupter. |
_ It has been suggested that the relative ionization would tend
to follow a density law as the rays became harder. The results
obtained in the present experiments do not give any indication of
such a result. Compared with air as a standard, methyl iodide,
methyl acetate and carbon dioxide shew a decrease as the rays
get harder in the relative amount of ionization produced ; hydrogen
and ethyl bromide, on the other hand, give a distinct increase ;
while ethyl chloride and carbon tetrachloride remain nearly
constant. The exceedingly small value obtained for hydrogen
with very soft rays (only 1°/, of that of air at the same pressure)
is very remarkable. The increase in the case of ethyl bromide,
the value for which for soft rays is already considerably above
that required on a density law, may also be noticed.
* Proc. Camb. Phil. Soc. Vol. xv. p. 34, 1908.
Réntgen Rays in different Cases.
TABLE.
Ri dain Meee Et
Soft rays Hard rays
eR Aes
PAGE aC akan 1:00 1:00,
Hee e “OL 18
(OO cosandoapcus 17 1-49
CH,CO,CH, . 4-95 3°90
CEH @ha u.5 2-0 18:0 17:3
COMER Sine 67 71
Cheba. yaa 72 118
(OJ G1 eer arte 145 125
Relative Ionization.
39
40 Professor Sims Woodhead, The Relationship between
The Relationship between Human and Bovine Tuberculosis.
By G. Sims WoopHEaD, Professor of Pathology.
[Read 23 November 1908.]
Before the infective nature of tuberculosis had been demon-
strated by modern methods there was considerable difference of
opinion as to the specificity of the tuberculosis occurring in
animals and in human subjects. Koch in his earlier observations
seems to have had little doubt as to the identity of the tubercle
bacillus in all forms of tuberculosis, though Klein at a very early
date held that the bovine tubercle bacillus differed somewhat from
that found in the human subject not only in its manner of growth
and in its relation to the tissues but also in virulence. Theobald
Smith, Dinwiddie and others as the result of a series of very
careful observations called attention to what they believed were
almost specific differences as regards size, mode of growth, virulence
and chemical products, between the human and the bovine types
of tubercle bacilli. During the time that I held the Grocers’
Company Scholarship I was led to make a careful examination of
the tuberculous material that fell into my hands with the view
of obtaining some light on the subject of caseation in tubercle
and of the relations of the various elements found in tubercle to
the spread of the disease not only amongst human beings but
amongst cattle. I was very early struck by the large proportion
of cases of abdominal tuberculosis (tabes mesenterica) met with
in extremely young children and after comparing my own observa-
tions with those already made by Bang, Rilliet, and Barthez I was
convinced that, in children at any rate, many of the cases of
tuberculosis were the result of a kind of natural infection through
the intestine. I found that in 127 cases of tuberculosis in
children on whom I had the opportunity of making a post-mortem
examination tubercular ulceration of the intestine was found in
forty-three. Only one of these cases had succumbed during the
first year after birth, but 14 died within two years and a half of
birth, 10 between three and five years, 7 from six to seven and a
half years, 5 from eight to ten years, and 6 between eleven and fifteen
years. Although there was tuberculous ulceration in forty-three
cases only, there was distinct tuberculous degeneration of the
mesenteric glands in no fewer than 100 cases or nearly 79°/, of
Human and Bovine Tuberculosis. 41
the whole. The age at which these tubercular glands in the
mesentery were found is significant. During the first year of life
there were 4 cases; from one to two and a half years, 33; from
three to five and a half years, 29; from six to seven and a half
years, 12; from eight to ten years, 13; and from eleven to fifteen
years, 9. In fourteen of these cases the mesenteric glands only
were affected, that is no tubercle was found in any other part of
the body. Here again more than half the cases appeared between
two and five and a half years. Since these figures were published,
Still, Shennan and the Royal Commissions on Tuberculosis in
this country and in Germany have published corresponding
statistics which in the main agree with those I have given and
I only use my own figures because they were the factor that
influenced, perhaps even biassed, my own conclusions. I should
now like to point out that whilst the child is suckled by its mother,
Le. during the first year after birth, it is not nearly so liable to
contract mesenteric trouble as at a later period; whilst during
the next two periods during which children are living on mixed
diet and, usually, are taking some milk from the cow, the number
of cases of tuberculosis rises very rapidly. Dr B. Hubermaas
studying tuberculosis of the breast pointed out that although
tuberculosis is so common in young married women, tuberculosis
of the breast is exceedingly rare. This observation has been
fully confirmed by later observers. It may, of course, be sug-
gested that tuberculosis is a disease of such slow development
that even if it were conveyed from other sources than by food and
by other channels than by the intestinal canal it would take some
time for the disease to manifest itself, and therefore would not
kill the child until it had reached an age beyond the first year.
It must be remembered, however, that in my investigation a very
careful search was made with the special object of finding tubercle
and that therefore tuberculous disease even though it had not
given rise to any symptoms during life would scarcely be over-
looked. I do not wish to minimise the importance of infection by
the tuberculous mother kissing and fondling her child, but this
factor (except that the process is not extended over such a long
period) is just as likely to be brought into play in the early years
of life, as later. We should not expect to have the very sudden
rise that we meet with if this were the only factor at work. It is
evident, however, that after the first year a second factor comes
in—food, in this instance milk, and so far as the reports of the
Royal Commission on Tuberculosis have been published and from
the reports from various laboratories there seems to be little
doubt that tubercle bacilli in enormous numbers are often present
in the milk that is supplied for human consumption. Quite apart
from anything else then, I am satisfied that these statistics as to
42 Professor Sims Woodhead, The Relationship between
mesenteric tubercle plus the presence of the tubercle bacilli in
such a large proportion of milk taken by these children are closely
associated.
Let us now come to another aspect of the question. All those
who have studied tuberculosis are satisfied that very numerous
and very distinct species are affected by tuberculosis, and as Sir
John McFadyean points out, we know of no single organism which
will produce disease in more than half a dozen:species and which
affects either the human subject or cattle which does not also
affect them both. It has of course been pointed out that the
tubercle bacilli met with in various animals exhibit very varying
degrees of virulence. They also differ considerably as to their
rate and luxuriance of their growth, and it is quite possible that
they may differ in other respects and perhaps differ very
materially. In this, however, they resemble many of the other
infective organisms. Washbourn and Eyre, for example, pointed
out that not only could they modify the virulence of the pneumo-
coccus by passing it through rabbits and mice, but that by
cultivating it as a saprophyte on sterile media in test tubes, they
were able to render its growth much more luxuriant and at the
same time to diminish its virulence, these alterations taking place
much more rapidly in certain of the individual organisms than in
others, as after cultivating them for some time they could separate
from the same culture highly virulent organisms, growing slowly,
and slightly virulent organisms, growing rapidly and luxuriantly.
Pasteur’s experiments on hydrophobia afford another example of
increase and diminution of virulence by passage through different
species of animals. Numerous observers have obtained similar
results by the passage of a streptococcus through different species
of animals; the streptococcus passed through the rabbit becoming
more virulent for that animal and less so for the mouse, whilst a
similar organism passed continuously through a series of mice
acquires increased virulence for that animal, this being accompanied
by a corresponding diminution in virulence of that organism for
the rabbit. It is unnecessary to multiply examples. Anyone
who will take the trouble to go through the appendix to the
Second Interim Report of the Royal Commission on Tuberculosis
will be very much struck by the marked differences in virulence of
the tubercle bacilli separated from different cases and inoculated
into animals. They will find that, speaking generally, the tubercle
bacillus, that is what the Commission terms “dysgonic,” is dis-
tinctly more virulent than the rapidly and luxuriantly growing ~
(eugonic) form. All varieties both as to growth and virulence have
been found in the human subject, some appearing to produce
extensive and rapidly generated lesions, others producing minimal
lesions or,in some cases, none at all. It is known that alterations
Human and Bovine Tuberculosis. 43
in temperature of nutrient media, etc. may affect the bacillus of
anthrax and render it almost inert, and that 1t may take some
time and special conditions for the restoration of the original
virulence. It is recognised too that the resistance of individuals
of the same species may vary enormously even to the same
organism, and that this comes out most markedly in the case of an
organism of modified virulence. If this holds good in the case of
the anthrax bacillus, may it not be equally true in the case of the
bacillus tuberculosis ?
Here we have to remember however that we have an organism
that grows comparatively slowly. In the first instance it sets up
localised lesions which in most cases at any rate are of slow
development.
A slowly growing organism and one that causes such com-
paratively slowly developing lesions will in all probability undergo
comparatively slow and slight modifications when it is placed in
new environments and is subjected to new conditions. The direct
evidence on these points is at present very small in amount and
unsatisfactory in character. We have little evidence of a morpho-
logical character. Pathologists have had so much to undertake in
connection with the study of the bacillus in the tissues and in
ordinary “culture” conditions that they have had little time or
opportunity to devote to the changes in morphological and
biological characters of the tubercle bacillus outside these two
limited areas.
The tuberculin reaction however has given us some evidence
that the differences insisted upon by Koch and his followers are
not specific, indeed are scarcely to be dignified by the term
varietal, but the large field of biological and morphological inves-
tigation that is just being broken, will I believe prove a most
fruitful field to men trained in these branches of study, and how
warmly their cooperation will be received it is scarcely necessary
for me to emphasise.
As far as can be gathered from the information now at our
disposal, the character of the lesions set up by different varieties
of the tubercle bacillus, the specificity of the reactions obtained
with tuberculin derived from bacilli derived from human and
bovine sources, the evidence slight though it be of modification of
morphological and biological characters, and especially the more
marked evidence of gradation of virulence in the two types as
usually described, we are, I think, justified in assuming that some
time or other we should be able to find links connecting even the
distant extremes, in spite of the great difficulties encountered in
tracing these links, difficulties that arise out of the comparatively
slow growth of the tubercle bacillus both in culture and in the
tissues, and the correspondingly slow development of the tuber-
culosis induced by them.
44 Professor Sims Woodhead, Human and Bovine Tuberculosis.
So far as mode of growth and lesions produced in the tissues,
size of organism, tuberculin reaction and all known characters
give us any lead we are I think bound to maintain that the
differences between bacilli obtained from tuberculous lesions in
the human being and those obtained from similar lesions in
cattle, are not specific, and that for this reason, the tubercle
bacillus, from whatever source it may be derived, constitutes a
distinct, and even grave, danger to any human or brute subject
to which it may gain access and I for one should be unwilling to
accept any responsibility for suggesting the relaxation of the
laws dealing with any thing in which this highly infective agent
is concerned. Indeed I would go further than this as I con-
sider it essential that it is our duty to do all that we possibly
can to strengthen the hands of Medical Officers of Health and
their Inspectors in the difficult task with which they are now
confronted.
Mr Purvis, The radiation of various spectral lines of neon, etc. 45
The radiation of various spectral lines of neon, heliwm and
sodium in a magnetic field. By J. E. Purvis, M.A., St John’s
College.
[Read 23 November 1908.]
Neon. The author had already photographed the principal
lines of neon vibrating in a magnetic field, when a paper by
Lohmann appeared giving a short account of the effect on the
lines when observed by means of an echelon spectroscope*: and
since then, Lohmann has completed the measurements}. He used
an echelon of 32 plates, the thickness of each plate being 1 cm.,
and the strength of the magnetic field was usually 11,000 units.
He states he was able to see and to photograph the lines divided
into 9, 12 and 15 constituents.
Field strengths were used in the author’s experiments of 26,100
and 24,000 units respectively, as the distances between the poles
of the magnet had to be adjusted to the diameters of the neon
tubes. In the first series of experiments, the first order of
Professor Liveing’s 21-foot radius grating spectroscope was used,
and, usually, there was an exposure of 20 minutes of the photo-
graphic plates. On examining the photographs with a low power
microscope, the author was unable to see the more complicated
divisions of some of the lines described by Lohmann.
Lately, the author has repeated the experiments with an echelon
of 18 plates, the thickness of each plate being 7$ mm.; and using
the same field strengths as were used in the Rowland grating
experiments. But, when the lines were divided into more than
three or six constituents, there was a great difficulty in distinguish-
ing clearly between the images of other orders and the images of
some of the constituents of the divided lines. For instance as
regards the line 6402, described by Lohmann as giving 15 con-
stituents, one could only be sure of five constituents; and of the
line 5944 divided into 12 constituents by Lohmann, four constituents
could be distinguished, of which there were two fairly sharp ones
* Physik. Zeits. 7 Jahrgang, No. 22, Seite 809—811.
+ “Beitr. zur Kennt. des Zeeman-phanomens,” Inaug. diss., Halle, 1907.
46 Mr Purvis, The radiation of various spectral
vibrating parallel to the lines of force, and two very diffuse ones
showing doubtful signs of division and vibrating perpendicularly to
the lines of force. The importance of this difficulty cannot be
exaggerated; for when the gas is vibrating in the magnetic field,
its luminosity is greatly increased; and the very faint images of
other orders, not clearly visible when the gas is not vibrating in the
field, would become better marked and clearer. The constituents
of these images would, therefore, interfere with a clear differentia-
tion of the constituents of any particular line under observation.
The advantage of Lohmann’s apparatus was the greater dis-
persive power of his echelon spectroscope of 32 plates as compared
with the one of 18 plates used in these experiments, and the
stronger field used in the present experiments did not appear to
compensate for the less dispersion of the echelon. So that until
the conditions of the experiments are more equal, no exact com-
parison of the observations can be made: and there is still the
more important difficulty of distinguishing the real constituents
of lines from the images of other orders. However, the distances
have been measured of the constituents of the lines unmistakably
divided into triplets, and, also, those of the line 6383 undoubtedly
divided into six constituents.
The diameters of the capillary parts of the neon tubes were
different, so that the distances between the magnet poles had to
be altered to accommodate them: and the strengths of the field
were 24,000 and 26,100 units respectively. The following table
gives the distances of the two constituents of the triplets vibrating
perpendicular to the lines of force from the one vibrating parallel
thereto, measured on the scale of vibration numbers, 1e. the
number of vibrations in a path of one centimetre*. The positive
signs denote the distances in the direction of greater wave length,
and s and p that they vibrate perpendicular or parallel to the lines
of force. It may be of use to workers in this kind of research to
state that the analysing Nicol prism should be placed between the
magnet and the quartz condensing lens when analysing the various
constituents of a divided line; for, if it is placed between the lens
and the slit of the spectroscope, the rotation of the polarised
constituents by the quartz lens produces a complete inversion of
the images when photographs are being taken in the ultra violet
part of the spectrum, so that the two outside constituents of a
triplet would appear to vibrate parallel to the lines of force, and
the middle one perpendicular thereto. It is possible that the
abnormal polarisations of certain triplets of various elements
which have been recorded have been produced in this way.
* Runge and Paschen, Sitz. d. Akad., Berlin, 1902 (1), p. 721, ‘“‘ Zeeman-efiect
entsprechender Serienlinien.”’
lines of neon, helium and sodium in a magnetic field. 47
Strength of field
’s 26,100 units.
4 i ak s
6717:2
—1, Boee 8
+ 0, i 8
6533°1
— 0, Sine Ss
+1, ae s
6266°66
—1, ene 8
+1 ne s
6163-79 x
—1, ae s
+1, A 8
607452 p
= Il oe s
+1, Bi s
5852°65 e
—1, ue s
Strength of field
24,000 units.
+ 1,126
0
~ 1,125
+ 0,766
0
— 0,788
+1,129
0
—1,134
+1,544
0
—1,518
+1,713
0
— 1,692
+1,161
0
—1,195
The line 6383°15 is divided into six constituents, and the
distances between corresponding constituents were measured.
Strength of field
26,100 units.
+ 1,804 s
+ 0,878 s
+ 0,878 p
6383°15 0
— 0,878 p
— 0,878 s
| 1,804 s
Strength of field
24,000 units.
+ 1,656
+ 0,812
+0,812
0
—0,812
—0,812
— 1,656
In order to compare these numbers with Lohmann’s, the follow-
ing table contains the values obtained when they are calculated
in terms of the strengths of the field.
48 Mr Purvis, The radiation of various spectral
Purvis Purvis . Lohmann
r DN adn dx :
SO | ee Bei
—4,73 s — 4,69 — 4,70
6717-2 0 p 0 0
+ 4,69 s + 4,68 + 4,70
— 3,125 — 3,11 — 3,13
6533°1 0 p 0 0
+ 3,10 s + 3,28 + 3,13
— 4,50 s — 4,70 — 4,40
6266-66 0 p 0 0
+ 4,53 s + 4,72 + 4,40
— 6,38 s — 6,43 — 6,07
6163-79 0 p 0 0
+ 6,07 s + 6,32 + 6,07
— 6,84 s — 7,13 — 6,80
6074:52 0 p 0 0
+ 6,59 s + 7,05 + 6,80
—4,78 s — 4,83 —4,74
5852°65 0 p 0 0
+ 4,78 s + 4,97 + 4,74
— 6,91 s — 6,90 — 6,63
— 3,36 s — 3,38 — 3,38
— 3,36 p — 3,38 — 3,38
6383°15 0 0 0
+ 3,36 p + 3,38 + 3,38
+ 3,36 s + 3,38 + 3,38
+ 6,91 s + 6,90 + 6,63
The agreement between these numbers is moderately close ;
the chief differences being the two outermost constituents of the
sextet from 6383; although the numbers obtained from both my
measurements are fairly comparable. Also, there is no very close
agreement between the numbers obtained from the triplet of 6163,
except that the numbers obtained from my own measurements
are comparable.
Lohmann did not appear to observe if there were any shift of
the lines towards the red end of the spectrum when the neon was
vibrating in the magnetic field. It would be difficult to do this
with an echelon, for it would be necessary to move the photo-
graphic plate and there would be a consequent source of error.
But, with this object in view, some photographs were taken by
lines of neon, helium and sodium in a magnetic field. 49
the author with the Rowland grating. To accomplish this, a
copper slide was attached to the slit of the spectroscope, and slotted
in such a way that, in one position, the upper half of the image was
cut off during the normal vibrations of the gas, and, in another
position, the lower half was cut off when the vibrations were under
the influence of the magnetic field. No other alteration was made ;
the position of the photographic plate was not altered; the neon
tube was not touched; and the discharge through the gas was
exactly the same in both series of experiments. The two images
were consequently photographed directly over each other; and the
following table contains the numbers, in thousandths of an
Angstrém unit, of the shift towards the red end of the spectrum
of the middle constituent of the triplets, as well as of the shift
observed in the sextet from 6383°15, produced by a field of
» 24,000 units.
Shift in thousandths Shift in thousandths
ON of an A.U. r of an A.U.
6717 + 90 6074 + 42
6533 +100 5852 + 32
6266 + 32 6383 + 60
6163 +101
Ss
The + sign meaning, as before, that the shift is in the direc-
tion of greater wave lengths.
Efforts were also made to measure the shifts of some of the
lines which give more than three constituents. For example,
Lohmann states that the line 6096 is divided into nine con-
stituents. On my plates, there are three diffuse constituents,
and there are doubtful signs of further subdivisions; but the
latter are not sufficiently well marked, so that the measurements
were made from the centre of the middle diffuse constituent.
The same remark applies to 6678 and 6506 which are stated by
Lohmann to divide into nine constituents, and to 6402 which
is stated to divide into 15 constituents. There is no doubt that
there is a shift of these lines towards the red end of the spectrum
when they are vibrating in the magnetic field, but for the reason
just stated, the measurements are not of the same degree of
certainty as those obtained from the above triplets.
r Shift in thousandths of an AU.
6678 +90
6506 +80
6402 +45
6096 +74
The numbers indicate that the shift is different for different
VOL. XV. PT. I. 4
50 Mr Purvis, The radiation of various spectral
lines; and these differences eliminate any sources of error caused
by a movement of the instrument. If there had been any such
movement, it is obvious that the shifts would have been equal.
_ There was a considerable increase in the luminosity of the neon
when it was vibrating in the magnetic field; and although the
times of exposure and the other conditions were the same, the
intensities of the unaltered lines when the gas was vibrating
normally were weaker than the strongest constituents when they
were divided. And in no case was the sharpness of the constituents
equal to that of the unaffected lines, so that there was always
some difficulty in measuring any shifts or separations.
With regard to the intensities of the normal undivided neon
lines it may be mentioned that my observations do not coincide
exactly with those of Baly* or Lohmann, as the following table
shows. But not much importance can be attached to observa-
tions of this kind, unless the differences are clearly marked; and
possible variations in the efficiency of the dyed emulsion in various
parts of the photographic plates should not be left out of con-
sideration, although there are some differences which may indicate
the influence of varying conditions of pressure and discharge in
the tubes, as for example, in 5852 and 6717.
Intensities
r Baly Lohmann Purvis
5852 bets 20 ne 20 9
5882 8 10 8
5944 10 Wd 9
5975 8 9 5
6030 10 9 6
6074 10 11 8
6096 10 12 9
6143 10 15 10
6163 10 11 8
6217 8 9 6
6266 10 10 9
6304 8 9 8
(6328 6 we belle ig
\ 6335 ie Ory ee anal
6383 8 10 sss 10
6402 10 20 te 15
6506 6 10 ae 10
6533 4 9 Bee 8
6599 4 2) 9
6678 = 3 al 9
6717 il 9 8
* +The spectra of Neon, Krypton and Xenon,” Phil. Trans. A. 202, 1904, p. 183.
>
lines of neon, heliwm and sodium in a magnetic field. 51
Also, in agreement with Lohmann’s observations, and opposed
to Baly’s, no neon line at 6328°38 was observed on any of the
plates; but, as in Lohmann’s neon, there was a well marked one
at 6335.
Sodium. When the discharge through the neon was going
on, the influence of the magnetic field was to force it against
the side of the glass capillary, so that small particles of the glass
were illuminated, and the D, and D, lines of the sodium in the
glass were seen quite clearly. The divided constituents of these
two lines were sharp and well defined, and they could be seen more
easily than when a sodium flame was placed between the magnet
poles. Lohmann used the same method in examining these lines,
and the following table contains the results of the values obtained
from my measurements compared with his, and also with those of
Runge and Paschen, who used a Rowland grating and a field
strength of 31,000 units*.
Lohmann Runge & Paschen Purvis
$ = es 10%. - — x 10”, ~ roo x 1038,
fo 22589". — 6,00 ~ 6,40
| 2,92 p — 2,97 43 16
D,. 5896-2] 4 0 0 Gea
| + 2,92 p + 3,02 + 3,16
ro Sols + 5,95 + 6,30
A135 5 S18 — 7,42
~ 4,43 5 — 4,53 — 4:95
| —1,46 p — 1,48 — 1,44
D,. 5890-2 0 0 0
+ 1,46 p + 1,48 + 1,44
+443 5 + 4,39 + 4,75
+ 7,35 s + 7,39 + 7,42
The agreement between these numbers is only moderately
good. It is difficult to explain the variations, for the ratio of
2:1 of the constituents of D, is fairly well maintained. The
values are the close mean of 12 separate measurements on three
separate plates; and no changes in the strength of the field were
observed during any of the experiments.
Helium. One of the neon tubes contained some helium, for
the triplet from the line 5875-618 was well marked in the photo-
* Sitz. der Berl. Akad. 1902, p. 722.
4—2
52 Mr Purvis, The radiation of various spectral lines, ete.
graphic plates, and the following table contains the numbers
obtained from the measurements of the separated constituents,
compared with those obtained by Rayleigh quoted by Lohmann
and by Lohmann himself.
Rayleigh Lohmann - Purvis
x Ges dn uN
= RORSUET x 10%. = x x 1018. = 2 x 24,000 x 108.
Helium [ i : i 4, ae mn re
S67 618 | + 4,09 + 4,33 + 4,58
Lohmann’s were eye observations, and they might not be so
accurate as photographic ones.
Furthermore, it may be that small variations in the amount
and nature of the constituents of the glass of the tubes produce
changes in the field between the magnetic poles; and it is conceiv-
able that some of the energy would be absorbed by these con-
stituents, so that the full strength of the magnetic field would not
act upon the gaseous particles of the vibrating gas. This view
may explain the differences which have been noted in the
numbers obtained when the Zeeman phenomena have been ob-
served in gases.
General Results.
The results of these observations are :—
(1) A comparison of the measurements of the constituents
of various divided lines of neon, helium and sodium observed with
an echelon grating by Lohmann and with a Rowland grating by
the author.
(2) The important difficulty in distinguishing the real con-
stituents of a divided line from those of the adjacent images of
other orders when an echelon grating is used for the observations,
particularly when the line is divided into more than three con-
stituents.
(3) The measurements of the shifts of the divided consti-
tuents of various neon lines towards the red end of the spectrum,
and that the shifts are different for different lines.
(4) A comparison of the intensities of the normal undivided
lines of neon with those of Baly and Lohmann.
I have to thank Professors Liveing and Sir James Dewar who
were good enough to lend me two tubes of neon used in these
experiments.
Professor Nuttall, Trypanosoma lewisi, etc. 53
The transmission of Trypanosoma lewist by fleas and lice.
By G. H. F. Nutratt, Sc.D., Quick Professor of Biology.
[Read 23 November 1908.]}
The author described experiments, conducted in the Quick
Laboratory, which demonstrated that Ceratophyllus fasciatus and
Haematopinus spinulosus are capable of transmitting Trypanosoma
lewist. In one experiment, 3 fleas, transferred from a diseased to
a healthy rat, gave a positive result. On the other hand, 30—60
lice were required for the transmission of the trypanosome. No
signs of any development of the trypanosomes were observed in
the bodies of the lice.
The presence of anticoagulin in the salivary glands of Argas
persicus. By G. H. F. Nurratt, Se.D., Quick Professor of
Biology.
[Read 23 November 1908.]
Experiments conducted with Mr OC. Strickland have shown
that the salivary glands and intestine of Argas persicus contain
an anticoagulin which is inactivated by exposure to a temperature
of 80°C. for 10 minutes. The organs of the tick do not contain
haemolysins.
54 Mr Dixon and Mr Hamill. Mr Dixon and Mr Harvey.
The mode of action of specific substances. By W. E. Dixon,
M.A., and P. Hamitt, B.A.
[Read 23 November 1908.]
The action of secretin was first analysed, and it was shown
that this substance produces its effect by chemical combination
with the proferments in the pancreas. It was suggested that such
substances of the hormone type have no direct action on living
protoplasm. Other evidence was brought to show that drugs
having a specific action on a definite tissue do not bring about
that effect by chemical combination with protoplasm or with
a constituent of the living cell. It was concluded that the mode
of action of Galenical drugs was different from that of the
hormones.
The action of specific substances in toxaenna. By W. EH. Dixon,
M.A., and W. H. Harvey, B.A.
[Read 23 November 1908. |
It was shown that certain toxins such as that of diphtheria
cause death by vaso-motor failure. It was found that in animals
atfected with such a toxaemia death can be greatly delayed by
the injection of normal saline solution. The action of drugs
becomes progressively less according to the degree of toxaemia;
those drugs which act on the central nervous system are the first
to lose their effect and those which act on muscle-fibre retain
their characteristic effect longest.
Mr Chittock, The Migration Constants, ete. 55
The Migration Constants of Dilute Solutions of Hydrochloric
Acid. By C. Cuittock, M.A., Trinity College. |
[Read 23 November 1908. ]
Introduction.
The experiments described in the present paper were under-
taken with the object of throwing light on the cause of the
abnormally low electrical conductivity of dilute aqueous solutions
of strong acids and alkalies. It has long been known that whereas
the equivalent conductivity of a neutral salt becomes approxi-
mately constant at great dilution, that of a strong acid or alkali
attains a maximum value ata dilution of about one-thousandth
normal, and then decreases rapidly as the concentration is still
further diminished. This decrease might be due to one of two
causes; first, to some interaction between the ions of the acid
or alkali and the solvent, which might lead to a decrease in
the amount of ionization or in the velocity of one or both of the
ions; or secondly, to some interaction with the small quantities
of impurity which are always present in the most carefully pre-
pared water.
It was thought that measurements of the migration constant
of an acid at varying degrees of dilution might be of assistance
in deciding between these alternatives. If a small current is —
passed for a given time through a solution of some acid such as
hydrochloric acid, hydrogen will be evolved at the cathode and
oxygen at the anode. ‘The total quantity of acid present will
remain unaltered, but near the cathode there will be a loss of
acid, and near the anode an equal gain. If it is assumed that
the whole of the conductivity of the solution is due to the ions
of the acid, measurements of these changes of concentration give
us the means of calculating the ratio of the ionic velocities of
hydrogen and chlorine. Such experiments would therefore enable
us to determine whether the abnormally small conductivity of
a dilute solution is associated with an abnormally small mobility
of one of its constituent ions.
Let u, v represent the velocities of the chlorine and hydrogen
ions respectively under unit potential gradient. Then the migra-
tion constant for the anion is given by p=u/(u+v). If a quantity
of electricity Q coulombs is passed through the solution, the
number of gram-equivalents of acid gained at the anode and
lost at the cathode will be equal to a where q (= 96440
coulombs) is the charge carried by one gram-equivalent of
either ion.
56 Mr Chittock, The Migration Constants of
Now let a definite volume V cc. of the solution round the
cathode be separated from the rest and stirred, this volume being
large enough to contain the whole region in which any change
of concentration has taken place. The concentration of this
portion will then be less than its original value by an amount
~ 1000 22
on = 1000 qV”
dn being measured in gram-equivalents per litre. By measuring
the change of concentration we can therefore find the value of p,
and hence that of u/v. A second determination of the same
quantity can be obtained in a similar way from the change of
concentration at the anode.
In determining the migration constants of very dilute solu-
tions, it would be quite impossible to measure the changes of
concentration by the ordinary methods of chemical analysis. The
measurement of the electrical conductivity of such a solution
affords however a sufficiently delicate method of obtaining its
concentration, and this method has been employed in the pre-
sent work.
The experiments here described show that the apparent value
of the migration constant of a solution of hydrochloric acid increases
considerably as the concentration is diminished. It was thought
that this result indicated a decrease in the velocity of the hydrogen
ion as the cause of the low conductivity of the solution. A re-
cently published paper by Whetham and Paine* shows however that
another explanation is more probable. These authors have carried
out a series of measurements on solutions of sulphuric acid, by
a method similar in principle to that which has been employed
by the present writer, and have found a change in the migration
constant, which is similar, though smaller in amount, to that
which has been obtained in the case of hydrochloric acid. They
find that the change can be expiained on the supposition that the
conductivity of the solvent water is partly due to the presence
of a salt formed from a weak acid and a weak base, such as
ammonium carbonate; this substance may be present in sufficient
quantity, owing to the absorption of atmospheric ammonia and
carbon dioxide. A small quantity of ammonium carbonate would
account for the observed change in the migration constant, and
also for the decrease in the apparent equivalent conductivity of
a dilute solution of acid or alkali. They therefore conclude
that their experiments give no evidence in favour of the hypo-
thesis that the velocity of the hydrogen ion becomes smaller at
great dilution.
The writer’s experiments on hydrochloric acid had not been
* Proc. Roy. Soc. uxxxt. A, p. 58.
Dilute Solutions of Hydrochloric Acid. 57
completed when the work of the above authors became known
to him. The results already obtained had shown a large increase
in the apparent value of the migration constant; the degree of
accuracy attained with the most dilute solutions was however not
very satisfactory. The experiments have not been continued,
since it appeared that no information as to the existence of any
variation of the true mobility of the hydrogen ion would be
obtained; a short account of the method and of the preliminary
results is however given.
Eaperimental.
In conducting migration experiments with hydrochloric acid,
it was considered advisable to keep the electrolysing current
quite small, in order to prevent any evolution of chlorine at the
anode; the values deduced from the anodic and cathodic changes of
ecncentration should then be equally trustworthy. For this reason
the vessel used to contain the solution was arranged in such a way
that a comparatively small volume of liquid near each electrode
might be separated from the rest; the resulting change in con-
ductivity would thus be greater than if the liquid after the
passage of the current were merely divided into two equal
portions.
The cell is shown in Fig. 1. The main portion consists of -
a glass tube 1:3 cm. in diameter, bent into the form shown, the
total length of the column of liquid from A, to A, being about
80 cm. The current enters and leaves the solution by the
electrodes A,, A,, which are of stout platinum foil, platinized
and subsequently heated to redness. B,C,, B,C, are two pairs of
electrodes which are used for measuring the resistance of the
solution, connexion being made through the narrow tubes D,
which are slipped over the platinum wires which support the
electrodes, and fixed by sealing-wax.
The upper end of each main tube is closed by the indiarubber
bellows #’, which forms an air-tight joint, and at the same time
allows the electrode A to be raised and lowered for the purpose
of stirring the liquid. The separation of the anodic and cathodic
portions of the solution is carried out by increasing the pressure
of the air at K; the effect of this is to depress the liquid below
the level of the bends at S, S, and at the same time to cause it
to rise at each end of the tube to some distance above the
electrodes B, C.
The solution is made up in the stoppered pipette M. A quantity
of distilled water is placed in it, and the required amount of a
standard solution of acid is then run in from a small filling vessel,
which is weighed before and after the operation. The pipette with
58
ll
sie a
Mr Chittock, The Migration Constants of
AMAT AUAAT
aT
I
Fig. 1.
Dilute Solutions of Hydrochloric Acid. 59
its contents is now weighed, and the concentration of the solution
ean thus be calculated when that of the stock solution is known.
Three such stock solutions were prepared; the strongest (‘2154
normal) was estimated by precipitation as silver chloride, and the
other two were obtained by diluting this with weighed quantities
of water. The water used had an average conductivity of about
10 reciprocal ohms at 18°C.
The cell was immersed in a tank of water, which was well
stirred and maintained at a temperature of 18°C. by means of
a toluene regulator.
The method of carrying out an experiment was as follows.
The solution was made up in the pipette UM, of which the delivery-
tube was ground to fit the upper end of the vertical tube P.
A current of air, purified from ammonia and carbon dioxide, was
then slowly drawn through the cell, being introduced through the
tube K and led out at G and H. The liquid was then run in
from the pipette up to a mark on the tube at P, the volume of
solution used being thus the same in all the experiments. The
pressure over K was now increased, so that the liquid covered the
electrodes B, C, and the resistance at each end measured several
times by means of a commutator and galvanometer.
The liquid was now brought back to its original position, and
a eurrent passed through the solution from A, to A,, usually for
about an hour. The current was obtained from a battery of about
40 storage cells, and was measured by balancing the E.M.F. across
the ends of a resistance included in the circuit (varying from
2000 to 30000 ohms according to the strength of the solution)
against the E.M.F. of a Clark cell. The current was maintained
at a constant value by adjusting the applied E.M.F. by means of
a potential-divider.
After switching off the current, the pressure at K was again
increased, and the separated portions of the solution stirred by
means of the electrodes A. The resistance was then measured at
each end, as at the beginning of the experiment.
Let R, R’ be the measured resistances at the cathode before
and after the passage of the current, k, k’ the corresponding con-
ductivities of the acid, and w the conductivity of the water. We
then have
i+w fk
ER
ok oR
and therefore Rica Re
where DR Rashes
60 Mr Chittock, The Migration Constants of
Hence, from the equation on p. 56, we obtain
1000p Se"
Q
_aV dn BR
OR ice ey
From the numbers given by Kohlrausch, a curve was plotted,
with n as abscissa and & as ordinate. This curve is a straight
line over the range covered by these experiments, and we may take
(k + w).
the value of a to be constant. The value of & corresponding to
dk
the known concentration of the solution was read off from the
curve, and the migration constant p calculated from the above
equation.
The volume V of the separated liquid was determined as
follows. The cell was placed in position in the tank, and filled
with water up to the mark on the tube at P. It was then
weighed. The separation was now carried out in the usual
manner, the electrode on one side removed and dried, and the
separated water extracted, the last drops being removed with
filter-paper. The cell was again weighed, and the difference of
weight gave the weight of water separated. The whole process
was then repeated for the other side of the apparatus.
The results of the experiments are given in the following
table. The concentration n of the solution is given in gram-
Current P
ue us and time ee
Cathode Anode Mean
1:405 x 10-° | -1120 np} se Os SG Mls "1705 ial
60 min.
6:07 x 10-4| :0847 2°86 x 10-4 *192 197 194
50 min.
5:82 x104| :0835 2°87 x 10-4 "195 188 192
50 min.
1:°633 x 10-4 | :0547 7°15 x 10-5 See 204 213
E 60 min.
1:035 x 10-4 | -0469 4-77 x 10-5 261 "252 -256
60 min.
1:006 x 10-4 | -0465 ASM elOme -268 282 ‘275
60 min.
Dilute Solutions of Hydrochloric Acid. 61
equivalents per thousand grams of solution, and the current in
amperes. The migration constant for stronger solutions of hydro-
chloric acid, as measured by chemical methods, is given by Jahn*
as 167, remaining the same for dilutions varying from 31 to 151
litres per gram-equivalent. The strongest solution used in the
present experiments was 712 litres per gram-equivalent.
From this table a few experiments have been omitted, in which
for some accidental reason the measurements on one side of the
apparatus were not trustworthy. The check given by the agree-
ment between the results obtained from the cathode and anode
was considered of great importance, for in such dilute solutions
absorption of impurities from the glass or from the air was very
likely to occur during the progress of an experiment. In fact
with the most dilute solutions there was generally a gradual
increase of the measured resistance with time, which became
ee
P
nr
“OR “OF 06 08 10 Iz 14 16. 18
20
Fig. 2.
more marked when the liquid was stirred. This increase of re-
sistance would however tend to increase the value of p deduced
from the measurements at the cathode, and to diminish ‘the value
deduced from the measurements at the anode. No experiment has
therefore been retained in which both results were not available.
The values of the migration constant have been plotted against
the cube root of the concentration in the diagram (Fig. 2). Jahn’s
value for the concentration n= ;4, is also given; it is marked on
the diagram by a circle.
“200
150
Discussion of Results.
The change in the migration constant is much greater than
that which has been observed by Whetham and Paine in the case
of sulphuric acid. It has already been remarked that the numbers
* Jahn, Zeitschr. f. Phys. Chem. vol. uvit. p. 641 (1907).
62 Mr Chittock, The Migration Constants of
obtained with the most dilute solutions are not very trustworthy,
mainly owing to the fact that the measured resistances did not
remain constant, but generally increased with time. We can
easily see however that the change is too great to be explained
by a decrease in the mobility of the hydrogen ion. It has already
been mentioned that the curve obtained by plotting the con-
ductivity & of a solution of hydrochloric acid against the concen-
tration n is a straight line which does not pass through the
origin ; it can however be made to do so by increasing the values
of & by a constant quantity, equal to 3°7 x 10~*. This “ corrected”
curve we may then take to represent the relation between & and n
which would hold if the acid were completely ionized, and the
hydrogen ion possessed its maximum mobility. From the difference
between the ordinates of the actual and the “corrected” curve
for any given value of n, we can find what reduction in the
velocity of the hydrogen ion would produce the observed dimi-
nution of conductivity. Making the calculation for a concentration
6 x 10-4(n3 = 084), we find that the decrease in velocity would
be such as to cause an increase in the migration constant from
‘167 (the normal value) to 170. The value given by the curve
(Fig. 2) for this concentration is 191. The theory of diminished
mobility of the hydrogen ion is thus seen to be insufficient to
account for the observed change.
Let us now consider the alternative hypothesis, that the in-
crease in the migration constant is an apparent one merely, and
is due to the presence, in addition to the acid, of some neutral
substance of which the velocities of the anion and cation are
more nearly equal to one another than are those of hydrogen and
chlorine. Whetham and Paine have calculated the effect of such
an impurity, and have shown that if the difference of mobility
of its anion and cation is small compared with the mobility of
the hydrogen ion, the migration constant is increased in the ratio
(ku + k'v)|(k + k’)u, where k, k’ are the partial conductivities of
the hydrochloric acid and of the second substance respectively,
u the mobility of the chlorine ion, and v that of the hydrogen
ion. If then we calculate from this result the value of & which
would give the observed rise in the migration constant, we find
k’=87 x 10%.
The conductivity of the water used as solvent in the two
experiments, in which the concentration was approximately
6x 10-* gram-equivalents, was 9°7 x 10” reciprocal ohms. It
is clear therefore that this water did not contain a sufficient
quantity of any neutral salt to produce the observed effect. It
was preserved in vessels of Jena glass or of platinum; the pipette
in which the solutions were made up, and the migration cell
Dilute Solutions of Hydrochloric Acid. 63
itself, were however constructed of soft glass. It is however
quite impossible that the conductivity of the water could have
been greatly increased by solution of the glass; in one case
a solution of which the strength was 1°63 x 10~* gram-equivalents
per litre was allowed to stand in the pipette for a period of three
days, and the conductivity at the end of that time did not differ
by more than 2 per cent. from Kohlrausch’s value.
The observed results can probably be explained if we suppose
that the principal impurity in the water was ammonia dissolved
from the air. The ionization of ammonia is small, even in very dilute
solution; when hydrochloric acid is added, ammonium chloride,
which is highly dissociated, is produced. The partial conductivity
of the ammonium chloride will then be considerably greater than
the conductivity of the original ammonia, and the quantity present
may be sufficient to produce the observed change in the apparent
migration constant for the solution.
It is interesting to note, that Whetham and Paine concluded
from their experiments that the impurities in their water prob-
ably consisted of ammonium carbonate together with an excess
of carbonic acid. Goodwin and Haskell*, in an investigation of
the conductivity of dilute solutions of hydrochloric and nitric
acids, found that different samples of water, although their con-
ductivities might be equal, gave solutions of which the conduc-
tivities were markedly different; the conductivity of the acid,
corrected for the effect of impurities, was however the same in
all cases. The large difference between the results of the present
experiments and those of Whetham and Paine is therefore prob-
ably due to the specific effects of different impurities, and affords
additional evidence in favour of the theory that both the change
in the migration constant and the drop in the equivalent con-
ductivity curve are due to an interaction between the acid and
the impurities present in the solvent.
The author desires, in conclusion, to express his thanks to
Professor Sir J. J. Thomson for his kind interest and encourage-
ment during the progress of the work.
* Goodwin and Haskell, Physical Review, Dec. 1904.
64 Prof. Thomson, On the Carriers of the Positive Charges, ete.
On the Carriers of the Positive Charges of Electricity emitted
by hot wires. By Sir J. J. THomson, M.A., F.R.S., Cavendish
Professor of Experimental Physics.
[Read 9 November 1908.]
A series of measurements of the values of e/m for the posi-
tively electrified particles given out by a strip of platinum wire
heated to incandescence were made by the method described by
the author in a paper on ‘Positive Rays of Electricity,’ Phil. Mag.
Oct. 1908. When the platinum had been kept for several days in
a high vacuum and heated repeatedly to incandescence, the value
of e/m for the great majority of the positively charged particles
was about 10*/27, showing that the mass of the particles was
about 27 times the mass of an atom of hydrogen. The masses
of molecules of CO and N, are 28 times that of an atom of
hydrogen, and these molecules could not be distinguished by
determinations of e/m. The spectroscopic examination of the gas
given off by the hot wire after prolonged heating showed that the
CO spectrum was bright while that of nitrogen could not be
detected. For this reason I think the carriers of the positive
electricity are molecules of CO and not N,.
After the platinum by long continued heating had been
brought into a state when the carriers had for the most part the
mass of a molecule of CO, hydrogen was let into the vessel and
the platinum foil made red-hot in an atmosphere of hydrogen, the
hydrogen was then pumped out; determinations of e/m after this
process had been gone through showed that the average mass of
the carriers was only 8 or 9 times that of the hydrogen atom,
thus the absorption of the light gas by the platinum had
diminished the average weight of the carriers to about one-third
of its original value; this | think shows that the carriers of the
positive electricity given out by hot metals are for the most part
the molecules of gas absorbed by the metal. I have much
pleasure in thanking Mr G. W. C. Kaye for the assistance he has
given me in making these experiments.
Prof. Thomson, On the Electric Theory of Gravitation. 65
On the Electric Theory of Gravitation. By Sir J. J. THOMson,
M.A., F.R.S., Cavendish Professor of Experimental Physics.
[Read 9 November 1908.]|
The view that gravitational attraction is due to a slight excess
of the attraction between unlike charges of electricity over the
repulsion between like charges is a very old one, indeed it seems
to have been regarded by some writers as almost a part of the one
fluid theory of electricity. The theory is an interesting one
because it involves the existence of effects which do not seem to
be hopelessly too small to be tested by experiment: some of these,
relating to the possible influence of the velocity of the attract-
ing bodies on the gravitational attraction between them, have
recently been considered by Lorentz. At the end of this paper
I shall indicate another result of the theory which is of so special
a character, that if it were established by experiment, it would
follow almost as a matter of course that gravity must be due to
something very closely connected with electrical action.
Before discussing this effect I will consider the theory from
the point of view of stresses in a medium between the attracting
bodies. In one form of electrical theory we suppose that the
stress in the ether is altered by the passage through it of lines of
electric force, in such a way that the tension along the lines of
force and the pressure at right angles to them is increased by an
amount proportional to the square of the density of the lines of
force. When we endeavour to use lines of electric force to describe
the state of the magnetic field or of fields through which electrical
waves are passing, I think there are considerable advantages in
regarding the lines of electric force from a somewhat different
point of view from that usually adopted in electrostatics. In
that subject it is usual to take as the lines of force due to say a
positive charge e at A, and a negative charge —e at B, as the
lines whose directions are the resultants of the radial forces
e/AP? and —e/BP?, radiating from A and B respectively. We
might however regard the lines of force as consisting of two sets,
one set being straight lines radiating from A, the other straight
lines radiating from B. We might, that is, regard the component
fields of which the actual field is made up as having an actual
physical existence, and suppose that it is the effect they produce
and not their structure which is modified when several of them
‘exist simultaneously in the same field. We can illustrate the
difference between the two methods by considering the case of
two parallel vertical planes A and B, A being on the left of B,
VOL, XV. PT. I. 9)
66 Prof. Thomson, On the Electric Theory of Gravitation.
the one having a positive the other an equal negative charge. On
the usual view, lines of force only exist between A and B, the
lines starting from the positive charge on A and ending on the
negative charge at B; the region to the left of A or the right of B
being free from lines of electric force. On the other view positive
lines of force start from A both to right and left, and also negative
lines of force from B. In the region between A and B we have
the positive lines in one direction and the negative in the opposite,
both giving a contribution of the same sign to the electric force ;
while on the left of A and the right of B the negative and the
positive lines run side by side in the same direction and, as far
as the electric force goes, neutralize each other's effect.
The advantages of the second method are most felt when the
electric charges are moving and there is a magnetic as well as an
electrostatic field, the magnetic force at any point being regarded as
due to the movement of the lines of electric force at that point, and
proportional to the vector product of the number of lines of electric
force and the velocity of these lines. Thus suppose the plate A
is rotating while B is at rest, on the second view of the disposition
of the lines of force in the field, all the positive lines of force
rotate with A, thus there is motion of these lines, and therefore
magnetic force throughout the whole of the field and not merely
between the plates A and B: and we know from experiments that
the magnetic force does exist throughout the whole region and is
not localized between A and B. If we take the first view that
the lines of force, due to the charges on A and JB, are confined to
the region between A and B, then the rotation of A would only
set these lines in motion in the space between A and B, this
motion would only account for the magnetic field between the
plates, and we should have to introduce further hypotheses to
account for the magnetic forces which as experiment shows exist
in the other regions.
If we consider the differences which exist between the
properties of negative and positive electricity, the negative being
located on corpuscles, the positive on bodies of atomic dimensions,
it does not seem by any means impossible that there may be
some difference between the positive and the negative lines of force,
at any rate the effects of such a difference seem a legitimate
subject for discussion.
Let us take the case where all the lines of force are parallel
to the axis of x, and suppose that through unit area, at nght
angles to #, there are P positive lines of force running in the
direction in which wz increases, V negative lines of force in the
same direction; then on the usual theory of stress in the medium, |
in which we do not distinguish between the effects of positive
and negative lines, these limes increase the tension along the
Prof. Thomson, On the Electric Theory of Gravitation. 67
lines of force by k(P—N) where k is a constant. If we dis-
criminate between the effect of positive and negative lines we
must replace this expression by
aP?+ BN? — 2yPN,
where a, 8, y are not necessarily equal to each other. On this
assumption let us calculate what would be the attraction between
two slabs of matter A and B. Suppose that for each unit of
surface of A there are P, units of positive electricity, NV, of
negative, while P, and JN, are the corresponding quantities for B.
Fig. 1.
If P is the number of positive lines of electric force through
unit area, V the number of negative, then we see that between
the plates ‘
P=4(Pi — P,), N=%4(N, — X,),
to the right of B, .
P=3(P,+P), N=3(N,+ N,),
to the left of A,
JE ol ley gees) N=—3(N,+N,).
The force on unit area of B towards A will be the tension in
the region between A and B minus that in the region to the right
of B, i.e. it will be equal to
{za(P,—- P,P +48 (NM, — N.Y — $y (Pi — P2) (MW, — ,)}
—{Za(P, +P, +48 (Ni + WP — dy (Pi + P2) (Ni +N,)}
=—aP,P,—BN,N.+y7(PiN2+ P.M) ...... (1).
Let us take the case when both A and B are electrically
neutral, i.e. when P, = N,, P, = N,, then this force will be equal to
{2y—(4+ B)} P, Ps.
68 Prof. Thomson, On the Electric Theory of Gravitation.
If we suppose that the atoms of the different elements are
electrical systems, and that each atom contains a number of units
of positive and also of negative electricity proportional to the
atomic weight, then P, and P, will be proportional to m,, mz, the
masses of unit areas of the slabs A and B, so that the attraction
between the slabs will be proportional to {2y—(a+ 8)} mm.
Thus the attraction between two infinite slabs will be proportional
to the product of their masses and independent of the distance
between them, it follows from this that the attraction between
finite masses separated by distances large compared with their
linear dimensions, will vary inversely as the square of the distance
between them.
If we take the number of positive units of electricity in the
atom as equal to the atomic weight, then using the electrostatic
system of units
Tee Ie
mM Mes
== OP Se 3} Se LO.
when m, and m, are measured in grammes.
Thus the attraction between the slabs
= {2y—(a+ B)} 9 x 10? mm.
The gravitational attraction between the slabs is
27 x 6°6 x 107-8 x mma,
hence if the attraction we are considering is the gravitational
attraction
2a x 66
2y—(a+ B)= ager: 10-*,
But a, B, y are all very nearly equal to 1/87, hence
2 ere —1:2 10-4,
If in equation (1) we put WV, = NV,=0, we see that the repulsion
between these charges is aP, P,,if we put P, = P,=0, the repulsion
is BN,N,, and if we put V,=0, P,=0, the attraction is yP,N,,
thus a is proportional to the force between two unit positive
charges, 8 to the force between two unit negative charges and y to
the attraction between a unit positive and a unit negative charge.
It is to be noted that unless a= @=y, we have to amend the de-
finition of unit charges usually given, as in this case, if the force
between two units of positive charge at unit distance is the unit
force, the force between two units of negative charge will not be
so. If we recognise these differences between positive and nega-
tive electricity the definition of an unelectrified body is a matter
Prof. Thomson, On the Electric Theory of Gravitation. 69
of some delicacy unless we have recourse to the atomic theory of
electricity, and define an unelectrified body as one which contains
equal numbers of positive and negative units of charge.
The weight of a body on this view depends only on the charges
of electricity it contains, thus if we suppose an atom of hydrogen
to contain one positive and one negative charge, the weight of an
atom of hydrogen would only be twice that of a corpuscle which
contains one negative unit, but the mass of the hydrogen atom is
1700 times that of the corpuscle, hence the acceleration of the
corpuscle under gravity would be 850 times that of an atom of
hydrogen, or 850 x 981; if the atom of hydrogen contained n
units of positive and n of negative electricity the acceleration of
the corpuscle would be - 850 x 981, hence on this view we should
expect the acceleration of the corpuscle under gravity to be very
much greater than that of ordinary matter. At present the
detection of an acceleration of the corpuscle as great even as
850 x 981 would seem to be beyond the powers of known methods,
but not so much beyond as to preclude the hope that with such
improvement as we may reasonably expect in the manipulation
of slow cathode rays it may ultimately be capable of investigation.
70 Prof. Thomson, On the Distribution of Electric Force, etc.
On the Distribution of Electric Force along the Striated Dis-
charge. By Sir J. J. Toomson, M.A., F.R.S., Cavendish Professor
of Experimental Physics.
[Read 9 November 1908.]
A Wehnelt hot lime cathode was used to produce the discharge
as it was found that at low pressures the striations produced in
this way were remarkably steady and bright and in consequence
made accurate measurements of the distribution of electric force
much easier than with the ordinary discharge. It was found that
just in front of the bright surface of a striation towards the
cathode there was a reversal of the electric force. This reversal
causes a great accumulation of ions in the part of the striation
nearest the cathode, the recombination of the ions in this region
will therefore be much greater than elsewhere and it is shown
that a very simple explanation of the formation and behaviour of
striations was given by the hypothesis that the recombination of
the ions was the source of the luminosity in the striations.
Vee
Le
ef
CONTENTS.
The Laas of Mobitity and Diffusion of the lons formed in Guo Media.
= PAGE ==
94° Se
36 28
By E. M. WELuIScH. (Communicated by Sir J. J. THORSON re
The Radioactivity of Rubidium. - By NORMAN CaMPBELt Se Th
On the Free Pressure in Osmosis. By UL. Vicar. (Communicated os
Sir J. J. THOMSON.) (Two figs. in Text) . Ne Ae a oe
Therapeutic Inoculation for Generalised Bacterial Infections. cy ie
Noon. (Communicated by Professor G. Sms WoopHEaD.) (Six
figs. in Text) ae es ;
On the examination of living leucocytes in vitro. re Constant PonpER. =
(Communicated by W. E. Drxon.) (Two figs. in Text) . Oe
On the Relation between Lonization and Pressure for Réntgen Rays im”
different Gases. By J. A. CROWTHER. (Communicated by Sir J. J.
‘THomson.) (Two figs. in Text) a aa en ee
On the Relative Ionization pr oduced by Rontgen Rays in difieeent Gases.
By J. A. CRowTHER. (Communicated by Sir J. J. THoMson)
The Relationship between Human and Bovine Tuber culosis. By Professor 8
G. Stus WOODHEAD . : . Ai nee es vies
The radiation of apna lines of neon, helium and sodium ina —
~ magnetic field. By J. E. Purvis es ee
The transmission of Trypanosoma lewase ee Jleas and ue eS Professor
Go. FS NuriAImS a oe eee 58
The presence of anticoagulin im i ie salwary glands of Ar gas POSE: on
By Professor G. H. F. NUTTALL 53
The mode of action of specific substances. By W. Ee Dior al 2
P. HAMIL ae RET ie eens Se a
The action of specific substances in toxaemia. By W. i. Dixon and - —~
W. H. Harvey — ‘ : a i Womb As
The Migration Constants of Dilute Solutions of He Te Acid. By :
~. ©. Currrocn.- (Two figs. in Text) : 55
On the Carriers of the Positive Chon ‘ges of Electricity emitted y hot wires.
By Sir J. J. THomson : 5 : ; a : . 64
On the Electric Theory y- oe: Gr avitation. = sir J J. J. THomson. (One fig.
in Text) Pee Ms Benes a a eae ee
On the Distribution of Electric Por ce along the Striated Dischar ‘ge By a
Sir J. J. THomson Se Ce peter es eee ov hece Gap eee en
13:
: is ys aoe. Preuss ali E . He oe : ;
rao See tre, I SS eR LIN BELFER ast
SASS T9 : re
i , DN a
OF THE a
CAMBRIDGE PHILOSOPHICAL
| SOCIETY. :
VOL. XV. PART IL”
(Leyr Term 1909.)
“Cambribee :
AT THE UNIVERSITY -PRESS,
- AND SOLD. BY
DEIGHTON, BELL & CO. AND BOWES & BOWES, CAMBRIDGE.
CAMBRIDGE UNIVERSITY PRESS,
“6. F, CLAY, MANAGER, FETTER LANE, LONDON, B.C.
1909
“Price Three Shillings —
May 21, 1909.
NOTICES.
i: Heppner for complete sets of the first Seventeen :
Volumes (in Parts) of the Transactions should be made to the
Secretaries of the Society.
2. Separate copies of certain part of Volumes t.—x1. of the
Transactions may be had on application to Messrs Bowns &
Bowes or Messrs DEIGHTON, BELL & Co., Cambridge.
3. Other volumes of the Z'ransactions may be obtained at:
the following prices: Vol. x11. £1. 10s. 6d.; Vol. x1. £1. 2s. 6d.;
Vol. xv. £1. 17s. 6d.; Vol. xv. £1. 12s. 6d. ;. Vol. xvi. £1. 10s. Od.;-
Vol. xvi. £1. 2s. 6d.; Vol. xvitt. £1. 1s. Od.; Vol. x1x. £1. 5s. Od. 5.
Vol. xx. £1. 10s. Od.; Vol. xx1. No. 1, 3/-; No. 2, 4/-; Nos. . a
4, 1/6; Nos. sande: 3/- 5 Nod, 2/-.
4. Complete sets of the Proceedings, Volumes L—XIV.,
may also be obtained on application to the Secretaries of the
Society.
5. Letters and Communications for the Society should be —
addressed to one of the Secretaries,
Mr A. E, SuHipLey, Christ’s College. [Biological.]
Dr E. W. Barnes, Trinity College. [Mathematical.]
Mr A. Woop, Emmanuel College. [Physical.] _ :
6. Presents for the Library of the Society should be sa
dressed to
The Philosophical Library,
New Museums,
Cambridge.
7. Authors of papers are informed that the Illustrations and.
Diagrams are executed as far as possible by photographic “process”
work, so drawings should be on a large scale and on smooth noe :
Bristol board in Indian ink. ;
8. Members of the Society are requested to inform the
Secretaries of any change of address.
PROCEEDINGS
OF THE
Cambridge Philosophical Society.
On a configuration of twenty-seven hyper-planes wm four-
dimensional space. By Professor W. BuRNSIDE, F-.R.S.
[Received 23 January 1909.]
[Read 9 February 1909.]
Clifford has shewn the existence of a plane figure con-
sisting of 2” circles and 2” points such that each circle passes
through n+1 of the points and each point lies on n+1 of the
ceircles*. If this figure be inverted with respect to a point outside
its plane, the circles become plane sections of the sphere into
which the original plane inverts. The configuration may then be
specified as one of 2” planes and 2” points, such that in each plane
lie ~+1 of the points and through each point pass n+1 of the
planes. The set of points is, however, restricted to lie on a sphere,
or, if the configuration is modified by a ores transformation,
on a quadrie.
That such a configuration exists, apart from the restriction of
the points to le on a quadric, is true; and I believe a proof of
the fact has been published though I cannot give a reference
to it.
In Mr Grace’s memoir a proof is given of the existence of some
very remarkable configurations of spheres and points in three-
dimensional space (pp. 182—188). If one of these, regarded as
existing in four-dimensional space, be inverted with respect to
a point, not in the three-dimensional space of the configuration,
* Clifford, Collected Papers, pp. 51, 52. See also J. H. Grace, ‘‘On circles,
spheres and linear complexes” (Camb. Phil. Trans. Vol. xvi. pp. 153-190), with
which memoir this note is more directly connected.
VOL. XV. PT, II. 6
12 Prof. Burnside, On a configuration of twenty-seven
there results a configuration of points and hyper-planes; a certain
number of hyper-planes passing through each point and a certain
number of points lying im each hyper-plane; with the restriction
that the whole of the points lie on a four-dimensional quadric. As
in the previous case this restriction is not a necessary condition
for the existence of the configuration. The object of the present
note is partly to prove this result in a particularly interesting case,
and partly to bring out the tactical analogy (which the numbers
suggest) of the configuration of 27 hyper-planes with the con-
figuration of 27 lines on a cubic surface.
To avoid the continual use of the word hyper-plane, a flat
manifold in four-dimensional space, determined by four points, is
called simply a plane; and when it is necessary to refer to one
determined by three points it is called a three-dimensional plane.
A quadric in four-dimensional space is determined by fifteen
points. Eleven points therefore determine four linearly inde-
pendent quadrics. Every one of a system of quadrics through
eleven points must therefore have five other common points.
This and the fact that four points determine a plane and four
planes determine a point forms the basis of the reasoning.
1. Ina four-dimensional space, consider a base-point O, and
five planes,
Ie ne pate toy
passing through it. On the line of intersection of each set of
three planes, mark a point distinct from O; and denote the
point on the line of intersection of 1, 2 and 3 by 123. (In this
symbol the sequence of the figures is immaterial.) Denote the
plane which passes through 123, 124, 134, and 234 by 1234.
(In this symbol again the sequence of the figures is immaterial.)
Then the five pairs of planes
12345; 21345; 31245: 41235; 5,1234
are a set of quadrics through 11 points, viz. O and the 10 points
123, ete. Hence they determine a set of 5 further points, which
lie on all the quadrics, so that 8 of the 16 lie in each plane. Of
these 5 then, one must lie on 1 and the other four on 2345. That
one of the five which lies on 1 cannot also lie on 2; and a suitable
notation for the five points in what follows will be
16, 26, 36, 46, 56,
(here the sequence of the figures is essential), where 16 lies in the
five planes
1, 1845, 1245, 12385, 1234.
The figure thus constructed is a complete one in the sense that
each point (and each plane) bears the same relation to the figure
hyper-planes in four-dimensional space. 73
as any other point (or any other plane). Through each point five
planes pass, as given by the table
Ob. 8a Thi) Cea Ae Ne
(Oe ee eo ah 1294 alloeye
MGR ALe 1, 1345, 1245, 1235: 1284;
and the points and planes admit simultaneous groups of permuta-
tions for which the tactical relations of this table are unaltered.
The order of this group is 2‘. 5!; and as it affects the planes it is
generated by
(1, 2345)(2, 1345);
(1, 2) (2345, 1345);
(1, 2, 3, 4, 5) (2345, 1345, 1245, 1235, 1234).
It contains an Abelian group of order 16, as a self-conjugate sub-
group, and in respect of this is isomorphic with the symmetric
group of degree 5.
2. ‘Take now six planes,
2a 3 eae Dee 0,
all passing through the base point 0; and on the 20 lines of inter-
section of each set of three mark arbitrary points 123, etc. With
each set of five planes, out of the six, carry out the above construc-
tion, so that there arise fifteen fresh planes 1234, etc.; and thirty
fresh points 16, etc. For convenience of reference the set of
(1 + 20 + 30 = 51) points thus arrived at may be denoted by S).
The figure so far is obviously not complete in the sense already
explained. That part of the figure which les in the plane
(three-dimensional space) 1, consists of 16 points, O, 123, ... , 156,
12, ..., 16 and 15 three-dimensional planes, viz. the intersections
of 2, ..., 6, 1234, ..., 1456 with 1. This is one of the figures
referred to in the introduction and is completed by noticing that
12. 18, 1455 15, 66
lie in a three-dimensional plane.
Take now 123 as a base point. Through it pass just six of the
planes connected with 0, viz.:
P25 9985 1 123845) 5 12855 9 1236.
On each of 19 out of the 20 lines of intersection of these planes
one point (besides 123) of the set S, he. Thus
Cie er 8 there lies 0,
I, 2, 1284 * 124,
IL, IRSA TASS - 16.
On the line of intersection of the three planes 1234, 1235,
1236 there is no point of the set S,. On this line mark an
arbitrary point 1°23’, distinct from O. With 123 as base point,
the six planes through it and the twenty points (including 1’2’3’)
on their lines of intersection, complete the construction of the
6—2
74 Prof. Burnside, On a configuration of twenty-seven
beginning of this paragraph. Of the thirty additional points that
arise it will be found that twenty-one belong to the set S), viz.:
145, 245, 345, 45, 54, ie 2Ah,
146, 246, 346, 46, 64, 13, 31,
156, 256, 356, 56, 65, 23, 32.
The remaining nine, adhering to the notation already used,
may be represented by
DAR aly 2p eli 65
Ie aye IS,
2/34! 23/5’, 2'3'6"
(the sequence of the figures is immaterial), 1’2’4’ being the point
common to the five planes
1234, 1245, 1246,
(24, 25,026.) 12273) and s(14n 5) 1G ie 2raa
Since 12, 13, 14, 15, 16 lie in a three-dimensional plane, the
two latter planes may be written
(21, 23;°24, 25, 26) 123), G2) 13) 4 1s lifs lies
Instead of 123 any of the twenty points of which it is one
might be taken to make the last construction, and whichever is
chosen one point must be arbitrarily chosen on a certain line
before the construction can be carried out. ‘The construction
however, having led to a point 1’2’4’ on the line of intersection of
1234, 1245, 1246, it is now possible to take 124 as a base point
and, without introducing any further arbitrary element, to carry
out the construction from this point. When this is done it is
found that of the thirty additional points that arise twenty-one
again belong to the set S,, and the remaining nine are
Laren) a IMM AVON oe,
1/4/37, 1/4/5", 146’,
2/4/3', 2/45", 2'4’6"
where 1’2’3’ is the point common to the five planes
1234, 1235, 1236,
(12, 13, 14, 15, 16, 1/2’4’) and (21, 23, 24, 25, 26, 1’2’4,).
Comparing this with the specification of 1/2’4’, it follows that
1’2’3’ is the same point as 1’2’3’.
Similarly 1'2’5’, 1/2’6’, 1’4’3’ and 2’4’3’ are found to be
identical with 1'2’5’, 1’2’6’, 1’4’3’ and 2’4’3’. Hence, the point
1’2’3’ having been once chosen, when the construction of the
beginning of this paragraph is carried out with each of the twenty
points 123, ..., 456 in turn, besides the set S, a set of just twenty
points (including 1’2’3’) and no more will arise
hyper-planes in four-dimensional space. 75
Moreover, since
(12, 13, 14, 15, 16, 1'2’3’, 1'2’4’)
is a plane, it follows immediately that the fifteen points
12, 13, 14, 15, 16, 1'2'3’, 1'2/4’, 1’2’5’, 126’,
1'3’4', 135’, 136’, 1'4'5’, 1'4’6", 1'5'6'
all lie in a plane. Call this plane 1’ and the other five that arise
in the same way 2’, 3’, 4’, 5’, 6’.
Through 16 pass the five ‘planes
V’, 1845, 1245, 1235, 1234.
On the lines of intersection of 1’, 1245, 1235, 1234, there
lie the points 26, 1'2’5’, 1'2’4’, 1'2’3', and the plane through
these points is the plane 2’. Hence from the configuration of
§ 1, the planes 1’, 2’, 3’, 4’, 5’ meet in a point through which
6’ must clearly pass. Call this point O’. There is then finally a
set of 27 planes, viz.:
TOBA oan sl BO Taare
1 a ASS i nai Yea O hea
and 72 points, viz.:
0,
MOS MOA eds oa ive 456,
HA hes, Minn ek eed , 56, 65,
12/3, DEANE hina. Ces Aa 4/5’6’,
Through each point pass six planes and in each plane le
sixteen points, and the configuration is complete. The relations
are given by the scheme
On er: RDS, Ano Gr
Ona V 2! 3, ‘4, De 6";
(DAB eee es Od 1234, 1235, 1236 ;
AUDIO; Piha... 5 4’, 5, 6, 1456, 2456, 3456;
RZ) hee 1, 1’, 1456, 1356, 1346, 1845;
7A Sota 2, 2, 2456, 2356, 2346, 2345.
A very slight modification in the notation, viz. the replacing of
the symbol 1234 by (56) (the brackets will prevent confusion
between the symbol for a plane and the symbol for a point) gives
these relations a well-known form. In fact with Schlafli’s nota-
tion for the 27 lines on a cubic surface, the table gives the
36 double-sixers that can be constituted from them. The tactical
analogy between the 27 hyper-planes and the 27 lines on the
surface is thus obvious; and the hyper-planes and points admit a
group of 51,940 permutations for which the relations given by the
table are invariant.
76 Mr Wilks, Note on some double fluorides of sodium.
Note on some double fluorides of sodium. By W. A. R. WILKS,
B.A., Caius College. (Communicated by Dr Fenton, F.R.S.)
[Read 8 February 1909.]
Many of the insoluble compounds by which elements are
quantitatively estimated are, as might be expected, found in
nature as minerals. Hence it was thought probable that if sodium
could be estimated by means of some simple inorganic compound
the latter would be found as a mineral. On considering the
simple minerals containing sodium, the only one which might be
suitable for the purpose appeared to be cryolite.
This compound has been artificially prepared by Deville (An.
Ch. Ph. (8) 59, 82, 1860) and by Baud. The former saturated
hydrofluoric acid by sodium carbonate and alumina in the propor-
tion of three molecules of carbonate to one of alumina, evaporated
and obtained the substance 3NaF.AIF;. The latter precipitated
a solution of aluminium fluoride by sodium fluoride and obtained
the hydrate of cryolite 6NaF.2AlF,;.7H,O. This hydrate is
gelatinous and is soluble in water to the extent of 352 gms. per
100 cc. at 16°C. Natural ecryolite which is 3NaF. AIF; has the
solubility 034 gms. in 100 c.c’s at 15°.
In order to find whether sodium could be detected as double
fluoride, aluminium was dissolved in dilute hydrofluoric acid in a
platinum dish until the acid was exhausted. On adding this
solution to a solution of sodium chloride a gelatinous precipitate
was obtained whose composition has not yet been determined. If
the sodium chloride was dilute, however, the precipitate did not
appear. It was further observed that boiling the solution facili-
tated the precipitation and that in this case the precipitate was
no longer gelatinous but crystalline. It was also found that
acids had a marked solvent action on the precipitate. After
these preliminary observations another mode of preparation of
the precipitant was resorted to.
Precipitated aluminium hydroxide which has been simply
dried by a filter pump was added to a small quantity of strong
hydrofluoric acid in a platinum dish. The hydroxide seems to
exhaust the acid much better than does aluminium itself, and in
the process of solution the moist hydroxide furnishes sufficient
water to form a solution of convenient strength. In order to get
the best results the hydrofluoric acid is allowed to stand for at
least two days in contact with excess of hydroxide. The complex
Mr Wilks, Note on some. double fluorides of sodiwm. 7
hydrofluoaluminic acid formed is then so stable that hydrofluoric
acid does not seem to be split off even on boiling. The solution
was in fact boiled in a test tube for half an hour without any
apparent action on the glass.
To diminish the concentration of hydrogen ions in the resulting
solution, an acetate must be added. The acetates of nickel or
copper can be used for this purpose as neither of these metals give
precipitates of double fluorides. Hence to the hydrofluoaluminic
acid solution an equal bulk of a cold saturated solution of copper
acetate is added. This solution is then boiled and any slight
precipitate filtered off. To this solution an equal volume of a
50 per cent. solution of alcohol is added. This makes the reaction
still more sensitive. Care must be taken however not to add too
much alcohol, otherwise a precipitate will be formed which appears
to be redissolved only with difficulty on adding more water. If
this precipitant has been carefully made the test for sodium can
be carried out in test tubes.
The test is carried out as follows. About 5 cc. of the precipi-
tant is boiled in a test tube and then the sodium solution added.
If the latter is strong there will be an immediate precipitate. If
it is very weak, however, it will be required to be boiled for some
time before the precipitate appears. To make quite certain that
the precipitation was not due to action on the glass a blank
experiment was carried out at the same time in another tube
without adding sodium chloride. In this case there was no pre-
cipitate. The test appears to be very delicate, one part of sodium
chloride in 20,000 parts of solution being readily detected.
The precipitate in these cases has not the composition of
eryolite. Analysed by heating with strong sulphuric acid and
weighing the sodium sulphate and alumina it seems that sodium
and aluminium are present in the atomic proportions of 1.1: 1.
Further analyses are however being carried out.
Pure potassium and ammonium salts are not precipitated
under the conditions stated above. The metals other than sodium
which give precipitates are silver, magnesium, calcium, strontium,
barium and lead.
Attempts are now being made to determine whether sodium
can be quantitatively estimated in this way. It has already been
proved that precipitation is almost if not quite complete.
It was considered possible that the elements related to
aluminium treated in the same way would give precipitates with
sodium. It was found that ferric hydroxide dissolved in hydro-
fluoric acid gave with sodium a light brown precipitate which has
not yet been examined.
Chromium and beryllium, however, fail to give a precipitate
even with concentrated solutions of sodium chloride.
78 Mr Vegard, An experiment on ionisation with y rays.
An experiment on ionisation with y rays. By L. VEGARD,
Cand. real. Universitetsstipendiat of the University of Christiania.
(Communicated by Professor Sir J. J. Thomson.)
[Read 8 March 1909.]
1. When a gas is ionised by Réntgen or y rays, we are led to
consider the action of ether waves or pulses upon the molecules of
a gas. In order to explain the small amount of ionisation it is
necessary to assume that the various molecules are in a different
position relative to the pulse. Several possibilities are discussed
by Sir J. J. Thomson in his book, Conduction of Electricity through
Gases. As a way in which the molecules can have a different
position relative to the pulse, he mentions the possibility that the
wave-front has a structure. There is, however, another manner
in which a different relative position could arise even when we
assume a continuous wave-front, namely if the molecule had
certain directions of ionisation.
The directions of the electric forces in a set of pulses travelling
in the same direction must lie within narrow limits, e.g., all nearly
parallel or perpendicular to a certain line. Now for a molecule to
become ionised it might be required that the electric force should
act in a certain direction relatively to some axis in the molecule, or
it might require a series of pulses along this same direction.
If such conditions were necessary for ionisation, it would
naturally cut down to a great extent the number of molecules
ionised by the rays. It might possibly not be the only condition,
but if in general n conditions, 1, 2, 3, ..., n, were necessary for ionisa-
tion, and if the probability for each of them were p,, po, ..., Pn, the
ionisation would be proportional to the product py, po, Ps, --.) Pn-
We see from this, that if the probability for the occurrence of one
of the conditions is altered a certain number of per cent., the total
amount of ionisation would be altered in the same proportion.
Thus if the action of the pulse within a certain angle relative to
some axis of the molecule were a necessary condition, the change
in the probability of the occurrence of this condition would affect
the total amount of ionisation proportionally.
If now the rays had a continuous wave-front, we might be able
to effect a detectable change in the probability of this condition.
Suppose a cylindrical ionisation chamber is traversed by a beam
of parallel rays perpendicular to the axis of the cylinder. If now
we add another beam of rays traversing the same space of air
Mr Vegard, An eaperiment on ionisation with y rays. 79
inside the cylinder, we should get a different amount of ionisation
according to the different angle between the two beams. Another
way of putting it is to say, that the ionisation with such rays
with a continuous wave-front would not be an additive property if
the molecules had some axis of ionisation.
For, as the wave-trains from one source in rapid succession
traverse the chamber, these wave-trains would ionise those mole-
cules that had a certain direction relative to the pulse, and if now
a second source was applied with waves mainly in the same
direction, a number of those molecules that otherwise would have
been ionised by the second source are already picked up by the
first. one. ;
2. It was from these considerations that I was led to undertake
the following experiment, the object of which was to find whether
the ionisation by y rays was strictly an additive property.
Experiments on the additivity of ionisation have earlier been
made by T. Noda*. In his experiments, however, the two sources
gave rays of a different kind, and further one of his sources was
radium giving out a mixture of rays, so that these experiments
were of no use for deciding this question.
Description of experiment.
3. The ionising chamber had the form of a flat cylinder
(length 4°9 cm., diam. 15°5 cm.). The ends of the cylinder were
made of aluminium plates, the tube itself of a thin aluminium
sheet. A circular aluminium plate was fixed inside the cylinder
perpendicular to its axis by means of an aluminium rod connected
to an electroscope of the Wilson type. The rod was surrounded
by a guard-ring which was connected to earth, insulated from the
rod by means of sulphur, and fixed to the chamber by a plug of
ebonite. The wires leading to the electroscope were surrounded
in the usual way by conductors connected to earth.
The ionising chamber was placed with its axis vertical upon
a small wooden bench fastened to the table. The y radiation came
from two sources of radium; one of them could be placed in a
fixed position, the other on a moveable arm capable of rotating
about a vertical axis coinciding with the axis of the cylinder.
Thus the angle between the two bundles of rays could be altered.
Each piece of radium was placed behind two slits formed by large
lead blocks, in such a way that the radiation from each source was
mainly restricted to the space between two parallel horizontal
planes cutting the ionisation chamber at about equal distances
(1 cm.) above and below the inner plate. The distances from the
* T. Noda, Proc. of Camb, Ph. Soc. Vol. x11. 1906, p. 356.
80 Mr Vegard, An experiment on ionisation with y rays.
sources to the centre of the cylinder were about 35 cm. The
a and § radiation was cut off by lead plates 3 mm. thick. In all
other directions the radiation was stopped by piles of large lead
and iron blocks forming a layer about 5 inches thick around the
radium.
The ionisation was measured by the saturation current between
the inner plate and the chamber, the latter being given a potential
sufficient for saturation when the inner plate had a potential
nearly equal to that of the earth. The procedure was as follows :
The air in the chamber was first exposed to the radiation from
one source (a) alone, and the saturation current measured; the
second source (b) was then placed behind the second slit, while (0)
was left unaltered, and the current measured ; then (a) was removed
and the measurements repeated. This operation was performed
for two different positions of the moveable source corresponding to
the angles, 90° and 180°, between the mean direction of the ray
bundles.
The saturation current is inversely proportional to the time ¢
required for the gold leaf to fall between the same two marks on the
scale of the electroscope. This, however, is only true when there is
no leak and the zero point corresponding to zero potential of the leaf
remains constant. The leak observed when all radium was removed
from the room was too large to be disregarded. The velocity of the
gold leaf due to the leak was found for different positions of the
leaf. From this the time 7 required for the leaf to move through
the scale interval on account of the leak could be found. If the
time actually measured is 7’, and if 7 is a small quantity, the time
t, corrected for leak, will be r= - ++ > The leak might, however,
be altered by the presence of radium in the room; by cutting off
the rays that went directly to the chamber the leak could be
estimated, and was found to be very little altered by the presence
of radium. It is, however, not necessary to know this part of the
leak, for we can assume that it is an additive property.
The condition for additivity can then be written:
rel Bib Bae aa
i eee Bday
In general this expression may be equal to some quantity e.
The quantity 6 = ¢ will then give a measure of the departure
from additivity.
The results of the measurements are given in the following
table :
= 0.
Mr Vegard, An experiment on ronisation with y rays. 81
Part I. Angle 180°.
1 1 1 1 A lt 1
Interval ty ty T ae. Ie ton’ ()
50 divisions | 0,1723 | 0,1394 | 0,0051 | 0,3168 0,3167 | 0,000
HOS 0,1739 | 0,1382 | 0,0041 | 0,3162 | 0,3122 | +0,013
OORT %: 0,1828 | 0,1451 | 0,0040 | 0,3319 0,3315 | + 0,001
HO e = 0,2231 | 0,1663 | 0,0065 | 0,3959 | 0,3965 | —0,002
BORE 0,1885 | 0,1450 | 0,0040 | 0,3374 0,3396 | — 0,007
AO. ge 0,1885 | 0,1452 | 0,0039 | 0,3376 | 0,3389 | — 0,004
Mean value 6=+ 0,0002.
Part II. Angle 90°.
1 1 1 1 Teepe | 1
Interval i! iy T i + i’ + a 6
40 divisions | 0,2237 | 0,1636 | 0,0052 | 0,3925 | 0,3922 | + 0,001
Ore iu., 0,2916 | 0,2393 | 0,0057 | 0,5366 | 0,5379 |—0,002
BO «4: 0,2917 | 0,2389 | 0,0048 | 0,5354 | 0,5397 | —0,008
Mean value 6 =— 0,003.
The time is given in- minutes.
The table shows that within the limits of experimental error
the ionisation of air with y rays is strictly an additive property,
and that, as far as the effect sought for is concerned, the experi-
ment has given a negative result.
considerations the result only shows that at least one of the two
conditions necessary for the effect must be wanting; but apart
from its connection with the previous considerations the result is
of interest in itself, as giving a property characteristic of ionisation
with v rays.
In view of the previous
82 Mr Purvis and Miss Homer, The absorption spectra of
The absorption spectra of solid tetramethylpicene and of its
solutions. By J. E. Purvis, M.A., St John’s College, and Miss A.
Homer, Fellow of Newnham College.
[Read 8 February 1909.]
From the products of the action of aluminium chloride on
naphthalene investigated by one of us (Homer, Trans. Chem. Soc.
1907, vol. xcr. p. 1103) there was isolated a new hydrocarbon whose
empirical formula was C,H... It was suggested that this sub-
stance was an alkyl derivative, probably tetramethyl, of dinaphth-
anthracene, C.. H,,.
In a later paper by the present authors (Homer and Purvis,
Trans. Chem. Soc. 1908, vol. xc, p. 1319), it was thought that
further evidence as to the constitution of this hydrocarbon might
be obtained from a comparative study of the absorption spectra of
its solutions with the spectra of solutions of the supposed parent
substance, dinaphthanthracene, and of picene the isomeride of
dinaphthanthracene. Benzene solutions of these hydrocarbons
were compared because picene and dinaphthanthracene are practi-
cally insoluble im alcohol. As a result of the investigation it
was found that the absorption curve of the hydrocarbon C,H.»
exhibited the same type of curve as picene, and therefore the
substance was considered to be an alkyl derivative of picene.
Some comparative experiments were conducted about the same
time, both with solutions in alcohol and in benzene, with the
solid and: with the vapour of the hydrocarbon C,H... With
regard to the solutions, V/1000 solutions in benzene and in alcohol
were taken and the absorption curves plotted m the same way
as is described in the previous paper (loc. cit.). The solid
hydrocarbon C,.;H»» liquefies at 49—50°C., so that it was quite
easy to melt a little of the substance on microscopic glass cover-
slips, by which a very thin layer was uniformly spread over the
surface of the glass: the layer was quite translucent. The glass
was then clamped before the slit of a spectroscope and the light of
a Nernst lamp, of an iron are, and of a condensed iron spark were
used as the sources of light. Photographs were taken of the
solid tetramethylpicene and of its solutions. 83
resultant absorption spectrum and they were compared with the
absorption spectra of the benzene and alcoholic solutions. It was
found that in the three series of experiments the substance showed
three absorption bands, but that the relative position of the bands
varied. The bands of the solid were moved more towards the red
end of the spectrum than those of the alcoholic solution, whilst
their positions in the benzene solution were between those of the
solid and the alcoholic solution. In order to compare the results
the following table gives the numbers of the three bands in terms
of the mean oscillation frequencies:
C.;H., solid 2264 2405 2537
NV/1000 benzene solution 2290 2424 2584
N/1000 alcoholic __,, 2304 2441 2590
The numbers for the benzene solution are extracted from the
before-mentioned paper by Homer and Purvis (loc. cit.). And
comparing the positions where general absorption begins the
numbers are:
C,H», solid 2182
benzene solution 2212
alcoholic __,, 2247
It is evident from these numbers that there was a shift in the
position of the bands and of the general absorption towards the
red end of the spectrum according to the density of the medium,
whilst in the solid state the shift was more marked still.
The rate of vibration of the molecules of the solute must be
affected by the molecules of the solvent, that is to say the more
dense the medium the greater damping effect will it have on the
rate of vibration of the dissolved molecules.
Now in the solid state the mean free path of the molecules is
more restricted than when they are distributed throughout some
solvent, therefore the rate of vibration of the molecules of the
substance in the solid state should be slower than when in
solution.
Assuming that the general absorption is due to the vibrations
of the molecule and that the selective absorption is caused by
intra-molecular vibrations of the atoms which are also affected by
the molecular vibrations, then conditions which tend to damp the
rate of the molecular vibrations, that is, which cause a shift in the
general absorption will also cause a corresponding shift in the
selective absorption of the substance.
The results obtained are in accordance with this view, for a
comparison of the positions of the general and selective absorption
of the hydrocarbon in alcoholic and benzene solutions and in the
solid state shows that for benzene solutions there is a shift towards
84 Mr Purvis and Miss Homer, The absorption spectra, ete.
the red end, and that this shift is more marked still for the
absorption bands of the solid hydrocarbon.
Endeavours were also made to observe the absorption spectrum
of the vapour of the hydrocarbon. For this purpose a small
portion of the solid was placed in a thick hard glass bulb of about
50 mm. diameter. The bulb was then exhausted of air and placed
in a special apparatus designed to heat the bulb equally in all
directions so that the density of the vapour would be the same at
every point. The light of an iron arc or of a condensed iron spark
was used for different observations, but it was found that the
hydrocarbon decomposed so rapidly that no results were obtained.
The vapour of the hydrocarbon exhibited a most beautiful blue
fluorescence, very intense at first but rapidly becoming weaker.
The decrease in fluorescence seemed to be proportional to the
decomposition of the hydrocarbon, as evidenced by the conversion
of the substance to a brownish tarry residue. The decomposition
may have been started either by the action of the small amount of
air left im the bulb or by the contact action of the heated glass.
We hope to continue the work on the absorption and fluorescent
spectra of the vapour of this and of other hydrocarbons.
Mr Purvis, The absorption spectra, ete. 85
The absorption spectra of concentrated and diluted solutions
of chlorophyll. By J. E. Purvis, M.A., St John’s College.
[Read 8 February 1909.]
(Pirates I—ITI.)
The general phenomena of the absorption spectra of solutions
of chlorophyll have been described by various observers, and refer-
ences to such work up to 1908 are included in Kayser’s Handbuch
der Spectroscopie, vol. 1v. But, so far as the author knows, there
are no recorded observations on the comparative spectra of equiva-
lent quantities of chlorophyll in strong and dilute solutions: and
the aim of this paper is to describe a series of observations which
have been made in this direction.
The well-dried leaves of fresh parsley were ground to a powder,
and the chlorophyll extracted with rectified spirit, filtermg the
insoluble portions. A portion of the strong solution was diluted
719°8 times with rectified spirit, and the strong solution was
placed in a glass cell of 5 mm. internal width, whilst the diluted
solution was introduced into a glass tube, with glass ends, 3599 mm.
long. The ratio of the dilutions was, therefore, as 1: 719-8, and
there was as much chlorophyll in the one solution as in the other.
The two solutions were exposed to the same source of light for
equal periods of time. The only alteration in the conditions was
that made necessary by the change of the small cell with the
strong solution for the long tube with the dilute solution; with
this exception, all the conditions were fixed and exactly the same
throughout the whole series of observations. The apparatus and
photographic spectroscope used for the observations have been
fully described in the Proc. Camb. Phil. Soc. vol. X11. pt. 111. p. 206,
in some experiments by the author on the absorption spectra of
concentrated and diluted solutions of didymium and erbium salts.
Description of photographic plates.
Unfortunately, it has not been found possible to reproduce the
phenomena observed on the original photographs with any close
degree of precision. The fault is particularly noticeable in the
weak band 2 565, which is unmistakeably clear on the original
photographs. The gradual changes, however, can be traced fairly
closely by comparing the changes of the bands X 538 and 2X 508
in the reproductions 1 to 9, and which are described in the cor-
responding paragraphs 1 to 9.
86 Mr Purvis, The absorption spectra of
1. These photographs were taken immediately after the
solutions were made. In both solutions the bands at 1588 and
2565 are of the same width and intensity. The 565 band is
very weak in the reproductions, but it is quite visible in the
original photographs. The general absorption in both begins at
about » 510.
2. The second series of photographs were taken after the
solutions had been standing for some hours. The band 1538 in
the dilute solution is more diffuse and weaker than the band in the
strong solution ; otherwise there is no change in the two solutions.
3. After standing twelve hours longer, the bands 1538 and
565 appear to be very like the last photographs. But in the
strong solution a faint band 1508 has appeared, which is not
visible in the dilute solution.
4. After standing twelve hours longer, the concentrated solu-
tion shows that the bands 1.538 and 1.565 are very like those in
the last observations: whilst the band 2508 is more clearly
marked. In the diluted solution, the bands 1538 and 1565 are
still weaker and more diffuse than the corresponding bands in the
strong solution, and 538 is particularly noticeable in this respect.
There is no band at 1.508 in the diluted solution corresponding to
that in the strong solution.
5. After standing twelve hours longer, the general appearance
of the bands is much the same as in the last series of observations.
But in the strong solution there is a gradual increase in the amount
of light coming through on the more refrangible side of the band
2508; and there is no such appearance in the diluted solution.
6. The solutions were allowed to stand four days longer. In
the strong solution the bands 565, 1.538, and 2 508 are like those
in the last series of observations. In the dilute solution the band
2 538 is weaker and more diffuse than the corresponding band in
the strong solution. The latter band is as well marked as at the
beginning of the observations. In the strong solution the band
2508 is now well marked, and is absent in the dilute solution.
Besides that, there is less general absorption of light by the strong
solution than the. dilute solution.
7. The solutions were allowed to stand two days longer. The
general appearance of the phenomena of the two solutions is very
similar to that in the last series of experiments.
8. After standing four days longer, photographs were again
taken, and they showed that the bands were very similar to those
in the last series of experiments; but the general absorption in
the strong solution was less than before, whilst that im the dilute
solution does not appear to have altered.
9. Finally, after standing fourteen days longer, the photo-
graphs show that in the strong solutions the bands 538 and 2 508
PLATE I,
1
Dilute solution
Strong solution
Strong solution
Dilute solution
(Se)
—565
—538
508
Dilute solution
Strong solution
Strong solution
Dilute solution
Dilute solution
Strong solution
Strong solution
Dilute solution
508
ue oe
Pier) IU,
19 GO ica)
cS oD =)
Yen}
Dilute solution
Strong solution
—508
Strong solution
Dilute solution
ide}
65
13)
—538
ms —508
Strong solution
Dilute solution
Mies
ie
concentrated and diluted solutions of chlorophyll. 87
are quite well marked: there are very faint traces of the band
d 565, and the general absorption has decreased very considerably.
In the dilute solution the band 2 565 is stronger, and the
band 2.538 is much weaker and more diffuse than the correspond-
ing band in the strong solution, and, in fact, it has almost dis-
appeared. In the dilute solution no band at 2508 appeared.
There is also a gradual creeping in of light on the more refrangible
side in the dilute solution when compared with the last series of
observations. The difference between the general absorption at
the beginning (1), and at the end of the observations (9), in the
dilute solutions is very small, whilst that of the strong solution is
very striking.
Discussion of the results.
As no effort was made to purify the chlorophyll, it is probable
that some vegetable acid was present: and, by the continued use
of the alcoholic solutions, a little of the spirit may have been
oxidised to acetic acid: for, at the end of the experiments, the
solutions were found to give a weak acid reaction with litmus
paper. In any case, the first series of photographs showed absorp-
tion spectra very similar to those described by Russell and
Lapraik (Jour. Chem. Soc. vol. XL1. (1882), p. 334). Their solutions
were obtained by the action of very dilute acids on fairly pure
chlorophyll. Assuming, therefore, that the solutions used in these
experiments show absorption bands characteristic of chlorophyll
solutions in the presence of a very small amount of acid, some
explanation is necessary to account for the gradual changes in the
bands and the general absorption of two solutions containing equal
amounts of chlorophyll, one of which was diluted 719 times that of
the other.
(1) The greater volume of the diluted solution might have
contained sufficient dissolved oxygen to oxidise the small quantity of
the dissolved chlorophyll. Against this argument is the fact that
although both solutions stood for several weeks in a well-lighted
room and with easy access of air, the changes in the strong solu-
tion were not in the same direction as those in the dilute solution.
It was the dilute solution which showed more general absorption
at the end of the experiments. If the primary cause of the changes
had been oxygen, the dilute solution might have been expected to
have undergone a greater change.
(2) The changes might have been caused by the action of a
very weak acid analogous to that which occurs by the decomposi-
tion of sugars and glucosides, whereby complex molecules are broken
down into simpler ones; but the same objection may be brought
against this explanation as against the last.
VOL, XV. PT. II. fi
88 Mr Purvis, The absorption spectra, ete.
(3) It is more probable that the changes may have been
produced by the differentiating effect of enzymes, like the
oxydases, dissolved from the parsley with the chlorophyll, some
of which are known to be very soluble in rectified spirit. In the
concentrated solution the enzymes would be in more intimate
contact with the chlorophyll than in the dilute solution, and
the consequent break down of the chlorophyll molecule would be
sooner effected. This suggestion would explain the less general
absorption of the strong solution than of the dilute solution after
they had been standing for some time, as well as the changes
in the appearance and position of the bands, although the
substances corresponding to the bands 2538 and 2508 do not
appear to have suffered much change in the strong solution.
(4) It is hardly likely that the dissociating force of the
solvent was a factor in the changes. The system was too complex
to explain them by this theory, for there was not only chlorophyll
in solution, but also, most probably, small quantities of other
substances.
The eee effect of the solvent on some dyes may be
mentioned in connection with the above-mentioned changes in the
chlorophyll solutions. For example, strong aqueous solutions of
dyes like eocine and magenta, when diluted in the same way as
chlorophyll, gradually and slowly lose their brilliant colour whilst
the strong solutions retain it. But the colours of the dilute
solutions are at once restored by a single drop of an acid like
hydrochloric acid, and there is no such reversion in the dilute
chlorophyll solution; so that the changes produced by dilution of
the dyes are not comparable with those of the chlorophyll solutions.
Mr Purws, The absorption spectra of mesitylene, etc, 89
The absorption spectra of mesitylene and trichloromesitylene.
By J. E. Purvis, M.A., St John’s College.
[Read 8 February 1909.]
The absorption spectrum of mesitylene in the ultra violet region
has been described by Hartley and Huntington (Phil. Trans.
vol. CLXx. (1879), pp. 257274). They noted a band between
X 275—2 245 in strong solutions. By diluting this solution in
the ratio of 1: 2000, the strong band is resolved into three small
sharp bands, which remain visible in a solution of 1 : 3000.
Drossbach (Ber. Chem. Ges. vol. Xxxv. (1902), pp. 1486—1489,
noted that general absorption occurred at 336, but this occurs
only in a very thick layer. He did not appear to have noticed
any bands.
Coblentz (Astrophy. Jour. vol. xx (1904), pp. 207—223), has
observed the presence of a considerable number of bands and lines
in the ultra red.
The author has compared the absorption spectrum of trichloro-
mesitylene with that of mesitylene, when equivalent quantities of
substances were in alcoholic solutions. He noticed that the bands
and the general absorption were shifted in the trichloromesitylene
more towards the red end of the spectrum when compared with
their positions in the mesitylene solution. For example, through
a thickness of 40 mm. of solution and N/1000 concentration the
strong band in mesitylene lay between X 269—A 254, whilst that of
the trichloromesitylene was between X 287—A 263. Also, a most
important difference was the greatly increased persistence of the
absorption curve of the trichloromesitylene as compared with that
of the mesitylene. The loading of the ring by the chlorine atoms
influenced the vibration of the molecule so that the absorption
band was shifted towards the red end of the spectrum and agrees
with the effect previously observed by Hartley m the case of
substituted compounds, and, at the same time, the persistence of
the band was greatly increased.
It has been shown by Baker and Baly (Jour. Chem. Soc.
vols. XCI. and XClII. p. 1122), that, in the case of pyridine, the intro-
duction of chlorine atoms into the nucleus not only shifted the
bands towards the red, but also greatly increased their persistence,
7—2
90 Mr Purvis, The absorption spectra of mesitylene, ete.
and the explanation was that such an introduction reduced the
residual affinity of the nitrogen atom, and thereby allowed greater
freedom of vibration or pulsation of the ring.
The author has pointed out in previous communications
(Proc. Camb. Phil. Soc. vol. xtv. (1908), pp. 381, 485 and 568)
that the persistency of the band in pyridine compounds is con-
ditioned to a considerable extent by the relative or spatial
positions of the imtroduced chlorine atoms as well as by their
introduction either in the nucleus or the side chains.
Now the increased persistence of this strong band of trichloro-
mesitylene is very similar to that of the chlorme compounds of
pyridine and several of its methyl derivatives, where the chlorine
atoms had entered the nucleus, and, unless we assume some
changing valency of the atoms of the benzene ring, it does not
seem easy to correlate the two series of phenomena.
But before any definite conclusion can be drawn from these
observations on mesitylene and trichloromesitylene, it will be
necessary to examine the absorption spectra of other chlorine
compounds of the former substance, both when the chlorine atom
or atoms are in the nucleus and when they are in the side chains.
All that can be said at the present stage of the investigation
is that (1) the strong absorption band of the trichloromesitylene is
shifted more towards the red end of the spectrum than the corre-
sponding band of mesitylene, and that (2) the persistence of the
band of the former compound is much greater than that of the
mesitylene.
Mr W. H. Foster, of St John’s College, was good enough to
make up the solutions of the two substances examined.
Mr Dobell, On a so-called “sexual” method of forming spores, etc. 91
On a so-called “ sexual” method of forming spores in Bacteria.
By C. C. Dose tt, B.A., Trinity College.
[Read 22 February 1909.]
Two species of Bacteria—Bacillus btitschli (Schaudinn) and
B. fleailis (Dobell)—are known which differ from all other Bacteria
in forming two spores instead of one in each cell. Before spore-
formation, the following remarkable phenomena are to be seen :
A large individual begins to divide into two, but the division
is never completed, and all signs of it are subsequently lost. The
granules (? chromatin) in the cell then show streaming movements,
arrange themselves in the form of an irregular spiral in the long
axis of the cell, and finally heap themselves up at both ends of the
organism to form the two nucleus-like spore-rudiments. Round
each of these, a spore membrane is formed, so that the two spores
when fully formed lie at opposite poles.
The process of incomplete division and subsequent fusion 1m-
mediately preceding spore-formation were considered by Schaudinn,
and also by myself, to represent a form of conjugation such as is
found in some yeasts, Heliozoa, etc.—that is to say, a conjugation
of sister-cells.
From further investigations upon Bacillus spirogyra, Bacterium
lunula n.sp. and other Bacteria, it now appears to me to be certain
that no “sexual” process really occurs in the disporic Bacteria. I
believe that what has really happened is that the last bipartition
in the life-cycle—the one immediately preceding spore-formation—
has become abortive, and is not as a rule completed. The disporic
individuals are therefore really double individuals—physiologically,
but not morphologically.
If this interpretation of the phenomena is correct, then it has
some interesting results: for instance, it has an important bearing
upon the problem of the affinities of the Bacteria. One of the
most important arguments in favour of the close relations of
Bacteria and yeasts is removed. It has also some significance
with regard to the problem of “sexuality” in the Protista and in
living beings generally.
A discussion of these problems, and also of some special points
(e.g. the nucleus of B. spirogyra, etc.), will be given in my full
account of this matter, which I hope to publish before long in the
Quart. Journ. Microsc. Sct.
92 Mr Punnett, On the alleged influence of lecithin
On the alleged influence of lecithin upon the determination of
sez in rabbits. By R. C. Punnert, M.A., Gonville and Caius
College.
[Read 22 February 1909.]
In 1907, Professor Russo, of Catania, published an account of
certain experiments* in which he claimed to have brought about
a great increase in the relative number of female young produced
by rabbits. The method consisted in the injection of lecithin
either subcutaneously or into the abdominal cavity. In the paper
referred to Russo gives particulars of 100 litters from injected
does as well as of another 100 litters in which the does were not
injected. The injected does produced 217 ff and 431 ¢ f,
as against 400 /'f and 287 $$ from those not treated, and the
author consequently claims to have raised the proportion of
females from 41°8 °/, to 56°5 °/, of the total offspring.
Such remarkable results have naturally attracted attention
and several criticisms have recently appeared. It has been pointed
outt+ that the statistics published by the author are not complete,
but that, as he himself states, only those litters from the animals
treated with lecithin were recorded in which the number of females
preponderated over that of males (cf. Russo, loc. cit. p. 367, foot-
note). Until the complete statistics are available, any conclusions
as to the effect of lecithin upon the proportions of the sexes must
necessarily be of doubtful value.
On other grounds Russo’s resuits have been recently criticised
by Heapet. Russo claimed to have distinguished histologically
between the ovarian ova destined to produce females and those
destined to give rise to males. According to him fatty matter is
present in the former though not in the latter, and he supposed
that the injection of lecithin resulted in a higher proportion of
ova containing fat, i.e. of female ova. Heape points out that there
are good grounds for regarding Russo’s male ova as ova which are
in some stage of degeneration and consequently not destined to
give rise to embryos of either sex.
* Atti Acad. Lincei, 1907, Serie 5a, Vol. vi. pp. 313—384.
+ Bateson and Punnett, Science, N.S., May 15, 1908.
+ Proc. Camb. Phil. Soc., Vol. xtv. p. 609.
upon the determination of sex in rabbits. 93
During the past year Russo’s experiments have been repeated
by Basile* with negative results. From six injected does he had
117 young in 17 litters, and of these 66 were ff and 51 were
22. He also bred 60 litters from nine rabbits which were not
injected, and of the 440 offspring 225 were / while 215 were
¢¢. Among the offspring of the uninjected the proportion of
females was actually slightly higher than among the injected.
Being desirous of repeating Russo’s experiments I wrote to
him in February, 1908, asking for certain details in his method.
He very kindly sent me the information for which I had asked,
and at the same time informed me that he had produced similar
results by feeding with lecithin in place of the injection. My
experiments were carried out in accordance with the details of the
feeding method of which he sent me particulars. An emulsion
was prepared by shaking up 5 grams of lecithim (Merck) with
1000 c.c. of physiological salt solution (65 °/,). The daily dose for
each rabbit was 20 c.c. of this emulsion made up into a paste
with meal, and the treatment was continued for three months
before the doe was put to the buck+. I also went on with it for
a few days subsequent to this. No difficulty was experienced in
getting the rabbits to take their daily dose, for they soon became
exceedingly fond of it and ate it greedily as soon as it was offered
them. During the past summer 10 does were treated in this way,
and they eventually produced between them 47 young. Of these
24 were ff and 23 were 22. From these and other does not
treated with lecithin I have had 18 litters with 103 young, and of
these 54 were ff and 49 were 2. In either series of experi-
ments the numbers are not large, but so far as they go they are
entirely opposed to the view that feeding on lecithin has any
influence on the relative proportion of the sexes among rabbits.
* Atti Acad. Lincei, 1908, Vol. xvu. 1, p. 643.
+ Here I would express my thanks to my friend Mr F. A. Potts for kindly feeding
the rabbits for me during a week when I was absent from Cambridge.
94 Messrs Jones and Tasker, A coloured thio-oxalate.
A coloured thio-oxalate. By H.O. Jonus, M.A., Clare College,
and H. S. Tasker, B.A., Emmanuel College. .
[Read 8 February 1909.}
In investigating the action of substances on oxalyl chloride,
(COCI),, in the hope that chlorine might be removed and C,O, be
produced, thiophenol and its metallic compounds were used, since
the easy formation of diphenyl disulphide renders these substances
good reducing agents. j
Sodium thiophenolate reacts violently with oxalyl chloride, but
in place of C,O, two molecules of carbon monoxide are produced.
The action of thiophenol itself is less violent. On mixing
equivalent quantities of oxalyl chloride and thiophenol a yellow
colour is immediately produced and hydrogen chloride is evolved.
The evolution of gas continues until the mixture finaliy sets to
a solid mass. By crystallization from ether long sulphur-yellow
prisms are obtained, melting at 119—120°C. The substance
distils unchanged at atmospheric pressure.
On treatment with aqueous potash the substance dissolves,
giving in solution potassium thiophenolate and potassium oxalate,
the colour disappearing.
This behaviour, coupled with the mode of formation, indicates
that the substance is diphenyl-dithio-oxalate, formed according to
the equation
2C,H,SH + (COCI), = (COSC,H;), + 2HCL.
On combustion ‘2857 gms. of the substance gave 6402 gms. of
CO, and ‘0951 gms. of H,0.
Observed percentages C 61:12 H 3°70.
Calculated for diphenyl-dithio-oxalate C 61°31 H 3°65.
The substance is the first member of the class of dithio-oxalates,
and is interesting by reason of its colour (which is undiminished
by heating in ethereal solution with animal charcoal or by repeated
recrystallization), since diphenyl oxalate and monothioxalic esters
are colourless, while glyoxal is yellow.
Messrs Jones and Tasker, A coloured thio-oxalate. 95
In order to see if C,0, could be obtained as the result of
decomposing this substance, it was heated in an evacuated vessel
with metallic sodium. The resultant gas was collected by means
of a Sprengel pump. There was a sudden rush of gas, in quantity
far short of the theoretical, and some deposition of carbon. The
gas was insoluble in water or potash but was soluble in cuprous
chloride and burnt with a blue flame. Its vapour density was
taken by weighing a known volume. It corresponded with that
required for carbon monoxide.
94°24 c.c. at 654 mm. and 16°C. weighed ‘1002 gms.
Vapour density (H=1) 145
Theory for CO 14
With concentrated sulphuric acid, carbon monoxide is again
given off and a purple colour is given which is characteristic of the
behaviour of diphenyl-disulphide under the same conditions.
Other coloured esters and several metallic salts of dithio-oxalic
acid have been prepared, and their properties and derivatives are
being investigated.
96 Mr Potts, Observations on the changes
Observations on the changes in the Common Shore-crab
caused by Sacculina. By F. A. Potts, M.A., Trinity Hall.
[Read 22 February 1909.]
Professor Alfred Giard, whose recent death all zoologists must
deplore, established a great reputation by the brilliance and versa-
tility of his researches. Perhaps his most noteworthy discovery
was that the Rhizocephala, a family of aberrant parasitic Cirri-
pedes, produce an extraordinary modification of the sexual
characters of the Decapod crustacea they infect*. The evident
results of the association are the dwindling of the reproductive
glands of the host and the effacement of already existing secondary
sexual characters (such as copulatory styles) and assumption of
those of the other sex.
Since Giard wrote, the nature of these effects has been clearly
set forth by Geoffrey Smith} for the case of the spider-crabs
(Brachyura oxyrhyncha). Perfect sterility and the disappearance
of the gonads results. The abdomen of the male becomes trough-
shaped, often completely resembling the female type. The first two
abdominal appendages modified as copulatory styles dwindle, and
on the other segments a varying number of swimmerets, charac-
teristic of the female, are developed. Modification in the converse
sense is not observed in the female, but that of the male evidently
indicates the development of a hermaphrodite condition: for male
crabs, which have undergone these changes, freed from the para-
sites and allowed to recover, may regenerate an ovotestis with
mature sexual products of both kinds.
This, then, is an example of extreme modification. The common
shore-crab (Carcinus moenas) when attacked by the same parasite
offers a case of slight or incipient modification. The short descrip-
tion we owe to Giard is vague on several important points, and
the common association of the shore-crab and Sacculina on our
own coasts}, also renders it desirable that another account of the
phenomenon should be given.
* «Ta Castration Parasitaire,” Bull. Sc. Dép. Nord. Ser. 2, Tome xvii. 1887,
p. 1, and Ser. 3, Tome 1. 1888, p. 12.
+ ‘“Rhizocephala,” Mon. 29, Fauna u. Flora des Golfes von Neapel, 1906.
+ In Plymouth Sound a considerable proportion of the shore-crabs are found to
harbour Sacculina. It is curious to note that in many localities, e.g. Liverpool
Bay and the Isle of Man, the parasite is rarely or never found.
in the Common Shore-crab caused by Sacculina. 97
In the first of two papers on “La Castration Parasitaire”
Giard mentions the fact that a certain alteration in the character
of the abdomen can be noticed in male shore-crabs attacked by
Sacculina. The diagrams which he gives show plainly that the
infected males often possess an abdomen broader than that usually
associated with this sex, yet not attaining the full trough-like
development of the female. It was Giard’s view that the female
might approach the male type when parasitised ; he does not here
however refer to any modification of the female. Though no
definite statement is made the reader of this paper is led to
assume that atrophy of the gonads takes place.
To understand the account of the changes in the sexual
characters, certain particulars of the life history need to be supplied.
The elucidation of the extraordinary development of Sacculina
is found in a brilliant paper by Delage*. The fertilised eggs
develop into free swimming Nauplius larvae. These fix at the
base of hairs on the carapace of crabs, and the almost disorganised
mass of cells which has resulted from histolysis of the larval body
passes through the gap in the carapace which the articulation of
the hair affords. It wanders through the body cavity, and even-
tually becomes attached to the intestine in the region of the
abdomen. Here it grows, absorbing nutriment from the blood,
and attains to the development of the adult parasite. The in-
ternal stage of development is terminated by a moult. For if
the Sacculina is ripe for emergence it is found that the part of
the parasite destined to become external has eaten its way through
the muscles and epithelium of the abdominal wall of the host and
when the chitinous exoskeleton is cast, this visceral mass emerges.
Connection with the internal root-system is maintained by the
narrow peduncle occupying the aperture which served for escape.
In crabs (Brachyura) the abdomen is clothed with a fairly
thick exoskeleton. It follows that when the new shell is formed
after the moult described above the Sacculina acts as a rivet and
prevents the fleshy part of the abdomen, in any subsequent
attempt at moulting, being withdrawn from its chitinous case.
The fact that a crab infected by Sacculina is prevented from
further moulting and consequently from growth after the parasite
becomes external is well known, but I consider it to be due to the
mechanical disability, which I have pointed out above, alone. It
might conceivably be a repression of growth occasioned by the
drain of nutriment for the parasite or the action of some specific
substance secreted by that organism. But if this were so we
might expect to find a tendency to inhibit the moult which intro-
duces the Sacculina to the external world, also at work. For
* Arch. Zool. Hxp., Ser. 2, Tome 11. 1884, p. 417.
98 Myr Potts, Observations on the changes
while the parasite is in its internal stage the change occurs which
finds expression in the modification of the secondary sexual
characters in the new carapace. Ifa change of this magnitude
can be induced in the early stages of parasitism we might also
expect that the effect on growth and moulting would be established
and the Sacculina prevented from ever appearing at the exterior.
There does not appear to be any evidence for infrequency of
moults in crabs with Sacculina interna. It may here be pointed
out that the hermit crab when attacked by Peltogaster* (a near
relative of Sacculina) still moults regularly, a fact we can easily
trace to the investment of the abdomen by soft skin which tears
easily and so detaches itself in moulting, round the base of the
parasite. The degree of modification produced in this case is
great, but Peltogaster does not mechanically prevent the shedding
of the exoskeleton, and growth appears even to be favoured by
the presence of the parasite.
The general nature of change in the secondary sexual characters
has already been indicated. The increase in the width of the
abdomen is exemplified in the following diagrams similar to those
which accompany Giard’s paper. It will first be noticed that
Male. Modified male. Female.
while all the segments of the female abdomen are freely moveable,
in the male the third, fourth and fifth are fused together. The
first evidence of modification in the infected male is the re-
established segmentation of the abdomen.
The degree of modification may be actually measured by
estimating the ratio of the breadth of the abdomen at the segment
to the length (5
in Fig. . The indices so given are as follows:
CD
Uninfected male crab 5(—"58
Uninfected female crab ‘90
Infected male crab which has suffered the maximum
amount of modification
* Q. J. Microsc. Se., Vol. 1. 1906, p. 599.
in the Common Shore-crab caused by Sacculina. 99
' The male crab with the largest index does not approximate
very closely to the female type, and those so markedly modified
are but a small proportion of the whole. A third of the crabs
measured could be called entirely unmodified, a proportion which
corresponds roughly with the quarter unaffected by the parasite
in the case of the spider-crab, and of the hermit-crab.
The number of crabs measured was 59, so that the series is
too small to be satisfactorily plotted in the form of a curve. Some
idea of the distribution may be gained by the statement that
37 possessed an index between ‘56—66, while that of the re-
maining 22 lay from ‘67 to ‘77. In the first group there were
11 with an index of ‘60, and in the second 5 with one of ‘72.
One point in Giard’s short account which I desired to test was
his assertion that the older (or larger) crabs were not subject to
modification. The average carapace breadth of the crabs of index
‘56—66 to be sure is 49 as compared to 4°5 of those from
‘67—77, but the figure for the index ‘72 is 4°6 and for ‘77 the
extreme limit of modification is 4°7. Occasional crabs of excep-
tional size are met with, with abdomina considerably broadened,
and my observations give practically no support even for the
statement that younger crabs are more liable to modification than
older individuals.
In the abdomen the effect of the parasite was distinctly less
than is the case with the spider-crabs. With the other secondary
sexual characters no alteration was experienced. There was no
diminution of the copulatory styles in size and no appearance
of the abdominal swimmerets which are characteristic of the
female.
In the female no change was ever detected in the abdomen as
a result of parasitism, and the swimmerets appeared fully as
well-developed and thickly fringed with hairs as in crabs free
from the Sacculina.
With regard lastly to the sexual glands of the infected shore-
crab, here again there is little alteration. The females never bear
eggs, and the ova in the ovary are as a rule small and white, and
devoid of great stores of yolk. In the uninfected male the testes
are lobulated organs, stretching on each side across the liver.
The development varies greatly even in normal specimens. The
vasa deferentiae follow, and speedily become wide tubes with a
very characteristic milky white appearance, due to the multitude
of spermatophores, each crammed with spermatozoa, which they
contain. Posteriorly the male duct opens on the terminal joint
of the last thoracic leg, at the end of a long fleshy penis.
In infected males a certain diminution in size of the testis is
often noticeable, but actual atrophy never takes place. There is
very little reduction in size of the vasa deferentiae, and they always
100 Mr Potts, Observations on the changes, etc.
preserve the normal appearance, containing spermatophores in
large number with ripe spermatozoa. The genital aperture is
never blocked up with chitin as occurs in the cases of extreme
modification, and the penis shows no tendency to disappear. In
fact it is quite clear that the effect on the reproductive glands is
only small—the most noticeable change being the failure of the
female to produce large heavily-yolked eggs. The male, it might
be supposed, could impregnate the female successfully were it not
that the presence of the Sacculina prevented copulation. It would
be interesting to observe whether infected males ever attempt the
sexual act.
In summarising emphasis must be laid on the low grade of
the modification. One organ only, the abdomen, is subject in the
male to a change of a rather striking nature, though the testis
continues to produce spermatozoa and the ducts to be filled with
spermatophores. It may be pointed out that the term “castration —
parasitaire,’ as applied to the phenomenon by Giard, is somewhat
misleading here as in other cases, for the modification of the
secondary characters is not associated with the suppression of
the gonads.
In Pachygrapsus marmoratus, the common shore-crab of the
Bay of Naples, another of the numerous hosts of Sacculina, the
modification of the abdomen of infected males is of the degree
described above, 2.¢. about half-way between male and female types.
In other respects the change is far greater than that in Carcinus.
The female swimmerets appear on the abdomen in more or less
complete sets (no mention is made of diminution of the copulatory
styles), and the gonads are greatly reduced and may entirely dis-
appear. The case of Carcinus is better compared with that of the
“stylopised” males of bees (Andrena)* which undergo considerable
external change, though throughout parasitism the testis of one
side remains fully developed, and produces spermatozoa.
* Perez. Mém. Soc., Bordeaux, T. 111. 1880, p. xii.
Mr Crowther, On the secondary Réntgen radiation, etc. 101
On the secondary Réntgen radiation from air and ethyl
bromide. By J. A. Crowraer, M.A., St John’s College.
[Read 25 January 1909.]
In a previous paper* I have shewn that certain gases and
vapours, and notably compounds containing arsenic or bromine,
give off amounts of secondary Rontgen radiation enormously
greater than that given off by air under similar conditions. Thus
the ionization produced in air by the secondary rays from ethyl
bromide is some 540 times greater than that produced by the
rays from air itself under similar circumstances. The rays from
ethyl bromide are much softer than those from air, and in a
recent paper Prof. Bragg+ has suggested that in this fact may
lie a possible explanation of what he describes as the “ startling
results obtained in the case of arsenic and bromine.” He points
out that the rays from an ordinary X-ray bulb are hard to sub-
stances of low atomic weight such as aluminium or air, but soft to
the elements of higher atomic weight such as copper or iron. The
secondary rays from air are of the same type as the primary rays.
The secondary rays from bromine however are of a much softer
character, and so, to quote Prof. Bragg’s paper, “are brought
within reach, so to speak, of air, which rapidly converts them into
cathode rays, so that there is a very large ionization.” He
concludes, finally, “that the very large secondary radiations which
some substances appear to give, therefore owe their magnitude
largely to the fact that the air in which they are measured is
sometimes ten to twenty times as favourable to them as to the
primary rays which produced them.”
I was, of course, not unaware of the increased ionizing power
of the softer rays from ethyl bromide as compared with those
from air, and in my original paper, I endeavoured to correct for
this fact, on what seemed to be, in the absence of direct evidence,
the reasonable assumption that the ionization’ produced in air by
rays of differing hardness, was proportional to the amount of
absorption undergone by the rays in the secondary ionization
chamber. The final values given in Column III, Table 1, of my
earlier paper are reduced on this assumption. With this correc-
tion the relative intensity of ethyl bromide compared with air
became 217, as given in the table.
The assumption on which this calculation is made has never
* Crowther, Phil. Mag. [6], Vol. xiv. p. 653, 1907.
+ Bragg and Glasson, Proc. Roy. Soc. South Australia, Vol. xxx1. Oct, 1908,
102. Mr Crowther, On the secondary Roéntgen radiation
been directly verified, and in the light of Prof. Brage’s interesting
suggestion, it was thought desirable to make some direct experi-
ments on the point, and to compare the relative amounts of
ionization produced by the secondary rays from ethyl bromide
and from air, in some gas not so unfavourable as air, to the
harder radiations.
Methyl iodide, and ethyl bromide suggested themselves as the
most likely for the experiments. The ionization produced by the
primary rays in both is very large, and their coefficients of absorp-
tion for the primary rays are also large. The values obtained for
ethyl bromide, however, vary less rapidly with the nature of the
rays than those for methyl iodide, so that comparable results
are more easily obtainable with it than with the latter. On the
whole, therefore, ethyl bromide was preferred; and the experiment
consisted in comparing the amounts of ionization produced in
ethyl bromide by the secondary rays from ethyl bromide, and
from air.
To Cells
To Gauges =~
To Electros ope
The apparatus employed was a modification of that used in
my previous researches* on the subject, and it will not be neces-
sary to describe it in any great detail. The radiating gas was
contained in a rectangular brass box A ; the primary rays entering
through an aluminium window C; while the secondary rays passed
* Crowther, Phil. Mag. [6], Vol. xtv. p. 653, 1907.
from air and ethyl bromide. 103
upwards through a second aluminium window d into the secondary
ionization chamber B. A portion of the primary rays passed out
through a third aluminium window e, into an ionization chamber
P where its intensity could be measured.
The secondary ionization chamber B was of a different form to
that employed in the previous experiments. It is very difficult
to obtain the “saturation current” across a cylindrical ionization
. chamber, with a central wire electrode, such as was previously
employed. An elementary calculation will shew that the field
near the outer cylinder is only a small fraction of the average
intensity between the electrodes, and so, to obtain saturation im
this part of the gas it is necessary to apply a potential between
the electrodes much greater than would be required in the case
of a uniform field. As ethyl bromide is a somewhat difficult gas
to saturate, the cylindrical form of ionization chamber was
abandoned in favour of the form shewn in the figure. The
central electrode is here a thin sheet of aluminium leaf stretched
on a circular frame of copper wire. It is insulated by a quartz
tube passing through an earthed guard ring; the latter in turn,
being insulated from the case (which is charged to a potential of
480 volts) by an ebonite stopper. The ends f, f of the chamber
are of aluminium foil which is held in position by a similar device
to that employed for the windows in the box A, and described in
a previous paper. The various joints are made air-tight by means
of sealing wax.
The chamber B is so placed with respect to A, that no secondary
radiation from the walls of the latter can enter it. The currents
through the two chambers B and P are measured by Wilson elec-
troscopes in the usual way.
The ionization chamber B is filled with ethyl bromide vapour
at some suitable known pressure (about 200 mm. of mercury).
The ratio of the currents through B and P is then measured with
the box A filled first with air and then with ethyl bromide vapour
at a known pressure. From the ratio of these two quantities we
can find the relative amounts of ionization produced in the loniza-
tion chamber B by the secondary rays from air and ethyl bromide.
Corrections have to be applied for the absorption of the secondary
rays from the gas by the aluminium windows d and /; and in the
case of ethyl bromide, for the absorption of the primary and
secondary rays in the gas of the gas chamber A. Finally we have
to correct for the fact that the air and ethyl bromide are employed
at different pressures. The various data required are known, and
have been given in a previous paper on the passage of Rontgen
rays through gases*, and the various corrections required can be
easily performed. In this way it was found that the amounts of
* Proc, Roy. Soc. Vol. uxxxi. p. 103 (1909).
VOL. XV. PT. II. 8
104 Mr Crowther, On the secondary Réntgen radiation
ionization produced in ethyl bromide by the secondary rays from
ethyl bromide was 162 times that produced in ethyl bromide by
the secondary rays from air under similar conditions. The corre-
sponding value when air was used in the secondary ionization
chamber was 543. It will thus be at once apparent that the
ethyl bromide is much more favourable to the secondary rays from
air than is air itself.
But although the coefficients of absorption for different types
of rays are more nearly equal for ethyl bromide than for air, they
are still not independent of the hardness of the rays. The coefti-
cient of absorption of ethyl bromide for the primary rays used in
these experiments, and therefore, also, for the secondary rays from
air, was ‘13; while its coefficient of absorption for its own secondary
rays was ‘38. Knowing the dimensions of the secondary ionization
chamber B, and the pressure of the ethyl bromide in it, we can
easily calculate the quantity of each type of ray absorbed by the
gasin B. The width of the chamber was 3°5 cms.; the pressure
of the ethyl bromide in it 210 mm. of mercury. The percentage
energy absorbed in the gas was, therefore, for the soft rays from
ethyl bromide 19:2°/,, and for the hard rays from air 12°4°/.. If
we assume that the amount of ionization produced is proportional
to the amount of energy absorbed, we thus obtain for the relative
amount of secondary radiation from ethyl bromide, compared
with that from air, the final value 105; a result which is just
about half that given in the original paper. Though thus con-
siderably reduced, the secondary radiation from ethyl bromide
still remains abnormally large. If we divide the relative secondary
radiation by the relative density (3°78) we obtain the value 28;
as against 1:0 for the lighter elements; 8:0 for stannic chloride;
and 8-4: for methyl iodide.
It may be noted that, as the penetrating power of the
secondary rays from stannic chloride, methyl iodide, and sub-
stances of low atomic weight is the same as that of the secondary
rays from air, the values obtained for the relative amounts of
secondary radiation from these substances compared with air are
not subject to any correction for selective absorption by the
medium in the secondary ionization chamber, and therefore need
no modification as the result of the present experiments.
It has already been mentioned that in my original paper the
relative ionizations produced in the air of the secondary ionization
chamber by the different types of secondary rays were corrected
on the assumption that the amount of ionization was proportional
to the absorption. It was not possible, however, to measure the
absorption of the different types of rays in air itself, the absorption
by air being too small to be readily appreciable. What was done,
therefore, was to measure the absorption of the rays by some
from air and ethyl bromide. 105
solid, and to assume that the ratio of the absorptions was the same
for solid and gas. The phenomena of the selective transmission
of the primary rays by air, which Bragg has pointed out in the
paper already quoted, were at the time far from clear, and unfor-
tunately tinfoil, a substance which does not shew this selective
transmission of hard rays, was employed as the absorbing substance,
and the values obtained for it were used in calculating the final
result. The ratio of the coefticients of absorption of the secondary
rays from ethyl bromide, and air, is for tinfoil approximately 2°8.
The ratio for air itself is undoubtedly much higher. As mentioned
above it is hardly possible to measure the absorption of air itself
for these different rays, the absorption in any reasonable distance
being so small; but filter paper suggests itself as being composed
of elements approximating very nearly in atomic weight to air.
The absorption of filter paper, therefore, has been measured for
the secondary rays from ethyl bromide and air; and the ratio of
the two coefficients of absorption for filter paper has been found to
be 5-4. Using this corrected value for the coefficients of absorp-
tion, and assuming again that the ionization is proportional to the
energy absorbed (that is to say in the case of air, where the
percentage absorbed is very small, to the coefficients of absorption),
we deduce from our original measurements of secondary radiation
made in air the corrected value 101, for the relative amount of
secondary radiation from ethyl bromide. This value agrees re-
markably well with the value 105 obtained for the same quantity
from the present measurements, using ethyl bromide as the
absorbing gas in the secondary ionization chamber.
Summary.
The relative amounts of ionization produced in ethyl bromide
vapour by the secondary Rontgen radiation from ethyl bromide
and air have been measured. From this, knowing the absorption
of ethyl bromide for the two kinds of secondary rays, the relative
intensity of the secondary radiation from ethyl bromide has been
calculated; and has been found to be 105 times that from air.
The relative absorption of the two kinds of secondary rays has
been measured for a substance of low atomic weight; and the
value obtained has been used to correct the original results for the
secondary radiation from ethyl bromide, which were obtained from
measurements made in air. With this correction, the two values
for the secondary radiation from ethyl bromide, obtained by
measurements made in ethyl bromide, and in air, have been
shewn to be in agreement.
In conclusion I wish to express my best thanks to Prof. Sir J. J.
Thomson for his kindly interest in these experiments.
8—2
106 Mr Laby, A string electrometer.
A string electrometer. By T. H. Lasy, B.A., Research Student,
Emmanuel College, Cambridge, Joule Student of the Royal
Society.
[Read 25 January 1909. |]
The minute force, 10-* dynes, that is sufficient to perceptibly
deflect a stretched silvered quartz fibre, is of the same order of
smallness as that acting on the gold leaf of the most sensitive of
the usual electroscopes. This suggested that the fragile and irregu-
larly shaped gold leaf might be replaced with advantage by a
silvered quartz fibre.
I constructed a very simple form of string electrometer, and
was testing it, when through Mr N. R. Campbell I learnt that
Dr C. V. Burton had designed a model of a similar instrument.
The Cambridge Scientific Instrument Company kindly lent me it
to test. The results given below were obtained with this instru-
ment, after it had been somewhat altered.
The Einthoven Galvanometer.
Einthoven has found that the movements of a stretched quartz
fibre subject to a varying lateral force afford a precise and delicate
means of measuring that stress. With his string galvanometer, in
which a silvered fibre replaces the usual suspended coil, he has
obtained photographs of the moving fibre on a falling plate using
a magnification of about 500. Even with this magnification the
motion of the fibre was so free from irregularities of an extraneous
origin that Einthoven has been able to subject the oscillograph
curves thus obtained to a minute analysis*. He has also followed
vibrations with a frequency of 3000 per sec. The lightness
(from 6x10 to 5x10-7gm. per cm.) and excellent elastic
properties of the silvered quartz make such results possible.
Description of the Instrument.
The string electrometer (see fig. 1) used in these experiments
consisted of two vertical insulated plates, A, B, 15 em. long by
‘8 cm. thick with their edges parallel and at an adjustable distance
apart.
* Kon. Ak. van Weten. te Amsterdam, vit. p. 210, 1906.
Mr Laby, A string electrometer. 107
These plates were connected to the ends of a battery, CD, the
middle of which was earthed. The silvered quartz fibre, EF,
is stretched parallel to and equidistant from the two plates A, B;
this position of the string relative to A and B is attained by the
lateral movement of its points of support, #, F’; while its tension,
which has to be kept very constant, is controlled by the screw SV.
Fig. 1.
The terminals of the middle cell M, of the battery C, D, were
connected to the potentiometer Rr, the middle of which was
earthed, while the connection to the fibre could be moved from R
to r, 2.e. its potential varied from —1 volt to 1 volt by steps of 1/50
of a volt.
As the fibre was not highly insulated, tests could not be made
with it isolated, so that the results given later, it should be pointed
out, were got with the potential of the fibre maintained.
The motion of the middle of the fibre was observed by means
of a microscope with a Zeiss achromatic objective A, and micro-
meter eye-piece No. 3. The tube length was such as to give
a magnification of 100. A slight illumination gave a sharp image
of the black silvered fibre on a bright ground.
108
Mr Laby, A string electrometer.
Properties of a String Electrometer.
The purpose of the tests was to find how:
(1) the sensitiveness,
(2) the oscillograph powers of the electrometer depended on
40.
80
20
Sensitiveness (deflection per volt)
i)
(0)
(a) distance of the plates apart,
(b) their potential difference,
(c) the tension on the fibre.
Plates 1-4om apart
Tereston on ttbre increases
From curve (tol
10 20 30 40
Potential difference between plates in volts
Fig. 2.
Plates far apart (1:1 em.). The plates were set far apart
(compared to the distance moved through by the fibre) and then
Mr Laby, A string electrometer. 109
the sensitiveness (deflection per volt) was observed for a range of
plate potential differences. With a new tension the same observa-
tions were repeated. In this way the equal tension potential
difference-sensitiveness curves (figs. 2 and 3) were obtained. The
2
50
Plates 67cm qoart 3
Tension Uurease
trom curve / lod
40
380
=
= 920
Oo
2,
=}
=
~~
(>)
(<b)
5 4
5, 10)
m
m
<b)
a
2 2
= e
‘a
9
Oo
nD
O 10 920 80 40 50
Potential difference between plates in volts
Fig. 3.
sensitiveness is expressed in eye-piece divisions per volt on the
fibre: one eye-piece division =-0012 cm. movement of the fibre
itself. These curves express many of the properties of the instru-
ment. We see from them that a high sensitiveness was obtained
with the fibre not very tight (curves 1, 2, figs. 2 and 3), which in-
creased with the P.D. between the plates to its greatest value in fig. 3
for 18 volts, when the sensitiveness was 60. There is a practical
110 Mr Laby, A string electrometer.
limit, as will be explained later, to the sensitiveness that may be
obtained by increasing the potential difference, or decreasing the
tension. With the plates at this distance apart the position of
the fibre was plotted against its voltage and the curve of fig. 4
obtained. It will be observed that one of these graphs is a
straight line, so that the deflection is proportional to the voltage
even for high sensitiveness, and for a wide range (for an electro-
scope) of voltages.
50
40
30
25
20
15
Deflection of fibre
or
2 ) “4 6 8 OL he ite KS
Potential of fibre in volts
Fig. 4.
Plates near together (6°6 mm. and 3°3 mm.). When the dis-
tance between the plates was reduced to 66 mm. and finally
to 33 mm. several properties of the instrument, to be seen in
figs. 3 and 5, came into greater evidence.
The chief change in the potential difference-sensitiveness
curves (fig. 3, plates at 6°67 mm.) is that smaller P.D.’s appear to
Mr Laby, A string electrometer. 111
give a larger sensitiveness for a given tension, or as is to be expected
theoretically the sensitiveness for a given fibre tension depends
on V/d?, where V is the p.D. and d the distance between the plates.
This could not be fully proved as the tension of the fibre did not
remain sufficiently constant. With the plates at 33 mm. apart
the deflection of the fibre as its potential changed became markedly
different. With the fibre tight its deflection was still proportional
to its potential (the straight line of fig. 5), but when slackened the
Position of fibre
Potential of fibre in volts
Fig. 5.
position, which the fibre took up for different potentials, is repre-
sented by the curve AB (fig. 5); on lowering the tension still
further the fibre had two stable positions and apparently an
unstable one not experimentally realisable. In other words, if the
fibre is slackened the sensitiveness increases, but for a decreasing
range of voltages : theoretically we pass through infinite sensitive-
ness to instability. This property of the instrument, which sets
a superior limit to its useful sensitiveness, is best grasped by
examining fig. 5.
In Mr C. T. R. Wilson’s* tilted electroscope, as is well known,
this property is used to obtain a high sensitiveness, the adjust-
ments (plate potential, tilt and length of gold leaf) are altered
* Proc. Camb. Phil. Soc. x11. p. 135, 1903.
112 Mr Laby, A string electrometer.
till the portion AB (fig. 5) of the deflection potential curve is
realised.
Characteristics of the String Electroscope.
The fibre will stand vibration and sudden large changes of
voltage without breaking. The instrument has been carried on a
bicycle without damage to the fibre.
Sensitiveness. No common standard of comparison has yet been
proposed for electroscopes. The unit of deflection used in this
paper is one division of the micrometer eye-piece: 1/5 of this
could be read with certainty. The closeness with which the
observations fall on curves shews that the unit chosen is not
unduly small. In fig. 4 (plates 66 mm. apart) a sensitiveness
of 50 divisions per volt is shewn. At the same time the curve
is nearly a straight line, i.e. the deflection is approximately pro-
portional to the voltage, and the p.D. between the plates was less
than 40 volts. The electrometer has been quite sensitive using
only 20 volts p.D.; such a small P.D. could be kept constant more
readily (by the use of Weston cells, say) than the larger ones
usually required for electroscopes and electrometers. On the
other hand, large voltages, which require to be constant, would
generally still be required, for example, to saturate an ionised gas.
With the plates at 3°3 mm. apart and a P.D. of 36 volts a sensi-
tiveness of 100 divisions per volt over a range of ‘4 volt was
readily obtained.
Oscillograph Uses.
I do not think, however, that the value of the string electro-
meter will lie especially in its sensitiveness. It is not difficult to
make a gold leaf electroscope highly sensitive over a small range.
But there is a distinct need now for an electrometer capable of
automatically recording rapid changes of voltage, in the study
of discontinuous phenomena in the direction indicated by von
Schweidler*. For example in the beautiful experiment of
Rutherford and Geiger of counting the number of a particles,
which arrive in an ionisation vessel, by the excursions of an elec-
trometer the smaller the free period of the electrometer the
better.
To test the oscillograph powers of the instrument, the plates
were placed 3 mm. apart at a P.D. of 120 volts, and the tension
* Congrés international pour l'étude de la radiologie et de Vionisation, Liége,
05.
Mr Laby, A string electrometer. 113
on the fibre increased ; the sensitiveness was then 50 divisions per
volt. Yet the motion of the fibre was dead beat, and it took up a
new position in less than one-tenth of a second. Since the move-
ments of a fibre can be readily recorded photographically the
instrument seems to promise well as an oscillograph. Further
experiments are being made on this use of it.
It should be recalled that all the above experiments were
made with a steady source of potential. Mr H. Darwin has de-
signed a new instrument in the light of the experience obtained
with this one; when it is finished more complete tests than these
will be made with it.
I am indebted to Mr Horace Darwin and Mr Whipple for
having lent me the string electrometer I used, and for having had
certain alterations made in it. I am grateful to Prof. Sir J. J.
Thomson for the encouraging interest he took in these experi-
ments.
114 Mr Taylor, Interference fringes with feeble light.
Interference fringes with feeble light. By G. I. Taynor, B.A.,
Trinity College. (Communicated by Professor Sir J. J. Thomson,
F.R.S.)
[Read 25 January 1909.]
The phenomena of ionisation by light and by Rontgen rays
have led to a theory according to which energy is distributed
unevenly over the wave-front (J. J. Thomson, Proc. Camb. Phil.
Soc. X1v. p. 417, 1907). There are regions of maximum energy
widely separated by large undisturbed areas. When the intensity
of light is reduced these regions become more widely separated,
but the amount of energy in any one of them does not change;
that is, they are indivisible units.
So far all the evidence brought forward in support of the
theory has been of an indirect nature; for all ordinary optical
phenomena are average effects, and are therefore incapable of
differentiating between the usual electromagnetic theory and the
modification of it that we are considering. Sir J. J. Thomson
however suggested that if the intensity of light in a diffraction
pattern were so greatly reduced that only a few of these indivisible
units of energy should occur on a Huygens zone at once the ordinary
phenomena of diffraction would be modified. Photographs were
taken of the shadow of a needle, the source of light being a
narrow slit placed in front of a gas flame. The intensity of the
light was reduced by means of smoked glass screens.
Before making any exposures it was necessary to find out what
proportion of the light was cut off by these screens. A plate was
exposed to direct gas light for a certain time. The gas flame was
then shaded by the various screens that were to be used, and other
plates of the same kind were exposed till they came out as black
as the first plate on being completely developed. The times of
exposure necessary to produce this result were taken as inversely
proportional to the intensities. Experiments made to test the
truth of this assumption shewed it to be true if the light was
not very feeble.
Five diffraction photographs were then taken, the first with
direct light and the others with the various screens inserted
between the gas flame and the slit. The time of exposure for the
first photograph was obtained by trial, a certain standard of
blackness being attained by the plate when fully developed. The
Mr Taylor, Interference fringes with feeble light. 115
remaining times of exposure were taken from the first in the
inverse ratio of the corresponding intensities. The longest time
was 2000 hours or about 3 months. In no case was there any
diminution in the sharpness of the pattern although the plates did
not all reach the standard blackness of the first photograph.
In order to get some idea of the energy of the light falling on
the plates in these experiments a plate of the same kind was
exposed at a distance of two metres from a standard candle till
complete development brought it up to the standard of blackness.
Ten seconds sufficed for this. A simple calculation will shew that
the amount of energy falling on the plate during the longest
exposure was the same as that due to a standard candle burning
at a distance slightly exceeding a mile. Taking the value given
by. Drude for the energy in the visible part of the spectrum of a
standard candle, the amount of energy falling on 1 square centi-
metre of the plate is 5x 10° ergs per sec. and the amount of
energy per cubic centimetre of this radiation is 1°6 x 10—* ergs.
According to Sir J. J. Thomson this value sets an upper
limit to the amount of energy contained in one of the indivisible
units mentioned above.
116 Mr Richmond, On the parametric representation, ete.
On the parametric representation of the coordinates of points
on a cubic surface in space of four dimensions. By H. W.
Ricomonp, M.A., King’s College.
[Received and read 8 March 1909.]
By a cubic surface in space of four dimensions is here under-
stood the locus represented by a homogeneous equation of the
third degree in five variables, and the problem considered is a
method of expressing the ratios of the five variables as algebraic
functions of three parameters. Should the cubic surface possess a
double point, projection with that point as vertex leads at once to
a solution.
If however the surface has no double point, take any straight
line Z which lies wholly on the surface ; six such lines pass through
each point and twenty-seven lie in every space of three dimensions,
at least three of the latter being real. Through Z and any point
P of the surface can be drawn an S,, whose intersection with the
surface will consist of the line Z and a conic, which must intersect
L in two points, Q, and Q,. Conversely, if any two points Q, and
Q. be chosen upon ZL, the tangent S,’s at Q, and Q, have in common
an S, which contains Z and a conic passing through Q, and Q,.
Thus if points of the line Z are determined by a parameter, ¢,
then to any two values of it ¢, and ¢, correspond two points Q,
and Q,, and consequently a conic passing through Q, and Q,.
Another parameter y will define each point of the conic, and thus
the coordinates of each point of the surface will be algebraic
functions of ¢,, @, and w.
In fact the equation
we + 2uvy + vz + 2ur + 2ou+ p =0............ (1),
in which X and yw are quadratic functions and p a cubic function
of x, y, 2, represents a quite general cubic surface on which the
line L, e=y=z=0 lies. A point on Z is determined by a
parameter ¢ if v=u.d¢; and the tangent S; at the point is
“2+ 2yh + 2¢*?= 0.
Thus on the S, common to the tangent S,’s at points where ¢
has the values ¢, and gy,
2:y:2:: dib,:—4(di + Go): 1;
and if in (1) we substitute z=z.¢,¢., y =— $z(¢, + g,) and then
write ud, —v=2.w, the problem is solved.
Mr Campbell, The study of discontinuous phenomena. 117
The study of discontinuous phenomena. By NORMAN
CaMPBELL, M.A., Fellow of Trinity College, Cambridge.
[Read 22 February 1909.]
§1. The application by Kohlrausch* by Meyer and Regener+
and by Geiger{ of von Schweidler’s theory§ of the discontinuities
in the emission of rays by a radioactive substance to the measure-
ment of the charge carried by an a particle opens up a new and
most important field of physical research. The ingenuity of the
method must always give great interest to their work, but it has
lost much of its immediate importance since Rutherford and Geiger!
have measured the same quantity by the more direct and probably
essentially more accurate method of counting the number of particles,
one ata time. The justification of the lengthy discussion of von
Schweidler’s method which is given in the following pages is two-
fold. In the first place, it is believed that the discussion by the
four authors first named of the principles according to which their
observations should be interpreted is neither exhaustive nor com-
pletely devoid of error, and that a more thorough discussion will
enable the results obtained by von Schweidler’s theory to rival in
accuracy those attained by Rutherford and Geiger. In the second
place, it should be remembered that radioactivity is not the only
discontinuous process which we study. The trend of modern theory
is everywhere to replace by discontinuity the continuity which was
the basis of the science of the last century. Any method which is
especially applicable to discontinuous processes is certain to be
fruitful of results in every department of investigation, and any
considerations which can be advanced in the elucidation of such
a method are not devoid of value; at the present time I am
engaged in an attempt to apply the method to a totally different
form of ionisation current. .
§2. It will be desirable first to put von Schweidler’s theory
in a slightly more general and a somewhat more accurate form.
The author of that theory used in his calculations Bernoulli's
integral of probability. Now the use of the integral calculus in
this case is open to the objection that it assumes that the number
of possible cases, the probability of which is considered, is so large
that it may be regarded as infinite. But the essential feature
* Wien. Ber. 1906, p. 673. + An. d. Phys. xxv. p. 757.
+ Phil. Mag. April, 1908, p. 539. § See Kohlrausch, loc. cit.
|| Proc. Roy. Soc. A. 81, p. 191.
118 Mr Campbell, The study of discontinuous phenomena.
of the phenomena that we propose to investigate is that they are
discontinuous, that is to say, that they are to be regarded as made
up of a finite number of events and not of an infinite number: in
some cases to which we may have to apply our theory it is by no
means certain that the number is even very large. By using the
integral calculus we assume in our mathematical considerations
the proposition which we deny in our physical considerations.
Accordingly we must confine ourselves throughout to finite
quantities.
Consider a series of s trials in each of which one of the
two mutually exclusive events A and B must happen. Let the
probability that A happens be p and the probability that B
happens be g. Then it can be shown easily that if 4 happens
m times and B m—s times, the most probable value of m is ps:
and further that the probability that A happens ps — & times is
'
S:
(ps — 2) 1(gs +a)!
We shall require the mean value of the ‘deviation’ 2 for
a very large number (c) of sets of s trials. There are three
chief forms of mean value, 2°, Remembering the
identities
Sv SHR
P gq? i
Cc (p + gy g=a nA moat q”
and = e(e- 1 (pt gyre te(p tg) g= Sw Anp g%
c!
where A, = —————-—
(c—n)!n!
we can easily show that, since p+q=1,
— ee as s!
e@= Xa geese gate
z=ps (ps — x)! (qs+ 2)!
= Spq
a
and that =|z#|= pe if s is large*.
The mean values a2? and x are the same as those given by
von Schweidler for the case when s is very large: but we see that
their form is quite independent of any assumptions as to the order
of magnitude of s, p,g. But the form of |x| is not so independent,
and no further use will be made of this mean.
* See Bertrand, Calcul des probabilités, chap. rv.
Mr Campbell, The study of discontinuous phenomena. 119
In calculating these means we have assumed that a ‘very
large number’ of sets of s trials are taken. It is desirable to
inquire how large the number must be in order to reduce the
probable error within any desired limits. The problem is very
similar to that of determining the probable error of the calculated
probable error of a set of observations. If s is very large, it is
well known that the expression given for the probability of a
‘deviation’ 2 may be reduced by Stirling’s theorem to an exponential
form, so that the probability that the value of w lies between a,
and 2,+dz is
fu ea? dz, where h= Oe
Nor V2nqs
Accordingly the probability of a given set of o values of , a, a,
Pee sien that 2-4 a+ 0 + >... 0," — oO? 1s
We shall find that our observations give us the value of
ca?= >a. h is then chosen so as to make the probability of the
occurrence of this value of Sw? a maximum: we find
= 578 or a? = 57 = spq, as before.
Accepting these values, we can find the probability that h has
the value h+uh: this probability is
h + uh dur)” en Gituh)? cg? = Kem,
\ Wor
h Sas
where C= oe dus) et oat
Vor
Hence the ‘measure of precision’ of fh is /n. In order that the
probable error may be less than 1°/,, /n must be greater than
100 or n greater than 104 In order to attain this degree of
accuracy we must take 10‘ sets of the series of s trials. We have
assumed that s is large, but since the expression for the probability
will be of nearly the same form whatever the value of s and since
we require only a rough value for the measure of precision, we
may apply the result to all values of s such as are likely to occur.
§ 3. Let us now apply this theorem to such cases as are likely
to occur in physical investigation. Suppose that a very large
number of events VT happen in a time 7. If we fix our attention
on a period 7 within 7’ and small compared to it, the chance that
any one of these events will happen within 7 is = it must be noted
VOL. XV. PT. II. 9
120 Mr Campbell, The study of discontinuous phenomena.
that the probability is the same whether the parts of 7 are adjacent,
so that 7 is continuous, or whether they are scattered at random.
Now the occurrence of the NZ events correspond to the
s trials, and the events A and B correspond to the falling of one
of the WT events respectively within or without 7. Hence
iT: Le
NT =s, P=p q=1l-p-
Then if observations are taken over o periods, each of length 7,
and if Nr4+.2,, Nr +a,,... Nt+., are the number of the events
which happen within the period 7 is the Ist, 2nd,... oth observa-
tions, we have proved that
#=NT.5.(1-p)-
7 F
If we make 7 small compared to 7’, we have
OB = NRA cseSosen coke ee (1)
In the particular case of radioactivity, 7’ is the time over
which the activity of the substance suffers no appreciable decay :
the VT events are the breaking up of VT atoms. If, then, we
had some instrument which would indicate the number of atoms
which break up during any period + short compared to 7, we
might discover the value of WV by taking a sufficient number of
observations and equating to Vr the sums of the squares of their
deviations from the means or ‘fluctuations. An electrometer
connected to an ionisation vessel which could be exposed for a
known time to the action of the rays from the substance would be
such an instrument. But it must be noted that, though the
absolute value of the mean ‘fluctuation’ /22= Nr can be made
as large as we please by increasing the period 7, the ratio of that
value to the value of the whole number of rays emitted during
: N ;
the period 7 is equal to nl and decreases with an increase of +.
Numerical calculation shows that (unless Rutherford and Geiger’s
method of magnifying the effect due to a single ray is employed)
no value for t can be found for which the mean fluctuation exceeds
the probable error in the measurement of the value of the total
current.
Accordingly all who have attempted to apply von Schweidler’s
theory have employed some balancing method by which the mean
total current is reduced to zero, so that the fluctuations become
fluctuations about the zero and only their absolute magnitude
need be taken into account. These may be made as large as is
desired by an increase in V and 7. Geiger and, before him,
Mr Campbell, The study of discontinuous phenomena. 121
Kohlrausch, balanced against each other currents due to two
independent radioactive sources. Since some doubt has been
thrown on Kohlrausch’s results by later workers no further reference
will be made to them. Meyer and Regener balanced the current
from one radioactive source by means of a Bronson resistance, to
the terminals of which a compensating potential difference was
applied. by a potentiometer arrangement. And these two arrange-
ments are examples of the only two principles which seem possible
in any measurements of this kind.
But it must be noted that, if a reading of the instrument
is taken while the rays are acting, this reading will not indicate
the value of the fluctuation at the moment of observation. The
instrument has inertia, and its indication at any time is a function
of the fluctuations during some finite period preceding the moment
of observation. In Geiger’s method it might be possible to get rid
of the inertia of the needle by removing the sources of rays after
a definite period of action and allowing the instrument to take
up a steady position before the reading is taken. But we shall
see that there are grave practical difficulties in such a procedure:
and the method is not applicable to Meyer and Regener’s ob-
servations by reason of the ‘inertia’ of the Bronson resistance.
Accordingly the problem before us is to determine the relation
between the observed fluctuations, which depend on the constants
of the instrument, and the real fluctuations which depend only
on the nature of the source. We will consider first the method
of Meyer and Regener.
Meyer and Regener’s method.
§4. Let a charge H be given to the electrode system when
the electrometer is at zero and at rest. If the capacity of the
electrode system be C, the resulting potential will be E/C. If
the current through’ the Bronson resistance is proportional to the
potential difference between its terminals, this potential difference
will diminish exponentially with the time, so that the potential
difference acting on the electrometer needle at a time ¢ after the
charge has been communicated is
E/C et
where p is a constant depending only on the nature of the
resistance.
Let I be the moment of inertia of the needle, uw the coefficient
of damping, k the coefficient of torsion and KV the couple acting
on the needle when the P.D. between the quadrants is V. (It is
assumed that the deflection @ is proportional to the steady P.D.
9—2
122 Mr Campbell, The study of discontinuous phenomena.
applied.) Then the equation of motion of the needle subsequent
to the communication of a charge # is
ae dé
: we 20g | ee a 2).
La ae ae K.E/C.e 0 (2)
Taking into account the initial conditions the solution is:
= Aerts Bett a Perth |. aah scene (3),
where
eee hy r
ea Ne alk we KE An peme
nes 27 ; eal Cas Sey: a—p’
pte — 40k _ pPpae
B= RPS a mney
All these quantities can be found by suitable experiments
on the electrometer and the resistance. Accurate determinations
of them would require some ingenuity and labour, but they can
be found with accuracy sufficient for the purpose of this research
by methods which will be obvious to everyone. (See § 10.)
It is easy to show that, subject to the assumptions made, the
effects of charges communicated at any times, 7), T:,... Tm are the
same as if the needle had been at zero and at rest at the moments
of communication. Hence the deflection at a time 7, which is
subsequent to the communication of all the m charges, will be
given by
On= yrsm (Ae-*(2-*) + Be-8(f-tr) + Pet)
al
Let us now change the origin of time to the time 7, which
is the time of observation. Writing ¢,’ for the time before the
moment of observation at which the rth particle was emitted,
we have
On > (Ae es Bets 4 Pert) i See (5)
= stm (ty) (Say): eda aden (6).
Or is a function Bi of the number of particles emitted and
the times at which they were emitted. In the case which we are
considering we do not know these times and hence cannot determine
the number directly from a single observation. But I shall proceed
to show that we can determine it from the average of a large
number of observed values of @ 7. (It will appear later why we
have to take the average of 7 and not of |@7|.) For the main
principle of the argument I am indebted to Mr G. H. Hardy,
Fellow and Mathematical Lecturer of Trinity College, Cambridge,
who points out that though no elaborate analysis is necessary for
Mr Campbell, The study of discontinuous phenomena. 123
the solution of the problem, interesting questions are raised in a
branch of mathematics which has received little attention.
§ 5. Let the period of observation be divided up into m periods
T= = such that f(¢,’) may be considered sensibly constant during
any one period 7. The total length of the period of observation 7
(that is the time from the moment of insulating the electrode to
that of taking the observation) will be considered to be the same
for all observations: but from the form of f(¢,’) it is clear that all
periods 7’ may be considered equal so long as aJ’, 8T and pT are
all large compared with unity.
Let y, be the number of particles emitted during the rth
period +r. Then, during any one period of observation, y, is a
function of r. In this statement the word ‘function’ is used in
the widest possible sense, and not in the restricted sense often
employed in analysis. Further, to each value of r during any one
period 7, corresponds one and only one value of y,. Let us write
NS ch COV ates Be (7).
The function $(7) has different forms in different periods T.
Let there be v periods of observation and let the form of ¢(r)
in the pth period be ¢,(r). Since $(r) can have a large number
of forms, a definite meaning can be attached to the expression
‘the probability that g(r) has the form ¢,(r)’: let ®, be this
probability.
Let Nr + 2,, Nt +,... Nt+ a, be all the possible values of
y: then ¢,(r) has m of these values during the m periods into
which 7 is divided. The probability of the occurrence of any
value x, is, by § 2,
(NT)! 7\Nr-2, T NG ee
ase NT = Ne — ay! (7) (1 7) ee UD
Hence the probability that ¢(r) has a definite m of the possible
values of y, that is, the probability that @(r) has a definite
form, is
Nii Nialalotsi Mint = Dil tneliee la heures ee (8).
Now it is important to notice, for this is the essential step
in the argument, that the value of ®, is not affected by the order
in time in which the definite values of x, occur. ®, is the same
if the values of z, are the same: it is not altered if z,=a, when
r=wu and a, when r=v, instead of a, when r=wu and a, when
r=v. That is to say, ®, is wholly independent of r.
Now if ¢(r) has the form ¢,(r), the corresponding value of
Po wal bs |
Grane Dail IM URE in meses es soe onions (9).
124 Mr Campbell, The study of discontinuous phenomena.
The probability of this value of 67 is ®,: hence the sum of the
values of 67 for the v periods of observation is given by
Sy Pp = vee PLS be(r) f(77)P --eeeees (10),
where the first sign of summation denotes summation with respect
to all the forms which ¢ (7) takes in the v periods.
§ 6. Now summation with respect to a large number of forms
of a function is not a process of which the methods have been
elaborated. The value of the right-hand side of (10) cannot be
found by a direct method, but it can be found by means of the
following artifice.
Expanding the squared factor in brackets we obtain
SO p= v EP Dyd pny Veny [Nr + Nr (a, + a9) + @p%6\ f 77) fF (87)
Since ®, is independent of r and s, we may reverse the order
of summation and write
Sy Pps v Boy Bey Spor Po lA? f(r) f(st)
+ Nr (x, + x3) f (rt) f (ST) + tps f (17) f (st)... (12),
where the inner summation denotes that we take the average
of the terms in square brackets over all periods of observation
before summing them for the periods into which a single period
of observation is divided. Now V7 is a constant and, as has been
emphasized already, the average value of x, or x; is independent
of r or s. The value of x, in any one period 7’ depends on the
‘value of r, but the probability that it will have that value is
independent of vr. Hence the average value of (a, + #,) OY 2,2
is independent of f(rr) f(st) and we may take the latter factor
outside the summation with respect to p. Further we may notice
that the average value of w, or x; is zero by § 2: hence the average
of (x, +s) is zero and the average value of w,a, is zero, except
when r=s. (It must be remembered that we are not taking the
average for different values of r and s, but the average for the
same values in different periods, so that no a, is a member of }a,.)
Hence our equation finally reduces to
Op =v (BoP EE Wert Fer) fer) + BSE P(r) BETi Dyna)
al
But >f_; ®,2,? is simply the average value of z,? for all periods 7,
that is, the average of w,? for a very large number (v) of cases
which are perfectly independent. By equation (1) above, the
value of this average is Nv and hence
Ly Ona {dy Do Nr f (rr) f (st) + So, Nr. 7? (r7)} ...4).
a
Mr Campbell, The study of discontinuous phenomena. 125
Since f(rr) is a continuous function of r, we may, with certain
reservations to be considered later, replace the summations by
integrations. Putting t=dt we find
i
1 asa t=T t=7 T
SG, = Op —N" | dt f(t) | déf+N[ dt fr()...(5),
J) t=0 t=0 t=0
or, remembering that
e*T=e Sle PT 0,
= VAR oN DS be lee 9 baulys) | polar legal
py Cy (i ae, PED s
p= N° ( +t | ae tsar aes =
§ 7. Op is the deflection of the needle from its zero position,
but it will be found more convenient to express (16) in terms of
the deflections of the needle from its mean position @7. If @’p
denote the deflection from this mean position
C= (Oa) ig? iyiceth os loceas (17),
or since >0’7=0
G2 = (Gras it eps aes ele (18).
But, by an argument precisely similar to that given above, it can
be shown that
Hence
= VANS PB? Pay MP2 DLA ip hee nist a
Geni set sat opt ae Ben een ...(20).
We have found a relation between the unknown JV (the number
of particles emitted per second) and the quantities 0° 7, A, B, P,
a, 8, p, which are known, except so far as the charge # is
concerned. H# may be eliminated by the device of Meyer and
Regener, who, by the use of their compensation method, measured
not 077 but (2) =A? The formula applicable to their experi-
2
ments is
Ae is B H Je fi 2A B 2BiP, fe 2PA
wel 2428 Op) 148) Sater Diate & (21)
= NT Aa By Fp a Ath :
Since # is a factor of A, B, and P, it disappears in the ratio
on the right hand of (21).
126 Mr Campbell, The study of discontinuous phenomena.
In passing it may be noted that the argument cannot be
applied to the determination of |@7|. For, in the place of the
square of the expression in brackets in (10) we should have the
modulus of that expression. The modulus cannot be expanded
in powers of the variables concerned and, accordingly, the order
of the summations cannot be reversed. But on this reversal hangs
the whole argument. In any case it would be advisable to avoid
making use of |@7|, for we have seen in § 2 that its value can
be found with accuracy only if Nr is very large.
§ 8. Before proceeding to discuss in detail the application
of this theory to experiment we must consider how far the
assumptions that have been made are likely to be fulfilled in
experimental conditions.
(1) We have assumed that 7 is small compared with T.
Since we have seen that the theory is true whatever the value
of Nz, it is clear that this assumption will cause no difficulty.
We have already, in replacing the summations of the last
paragraph by integrals, made 7 infinitesimal in comparison with
the time constants of the instrument. But T is the whole period
over which the physical conditions are constant, and it is clear
that the experiment will be arranged so that these are constant
over a period long compared with the time of observation.
(2) (1) is the only condition which is essential to the theory,
but we have seen that in order to get a probable error less than
1°/,, we must take a very large number of observations. The
quantity v corresponds to the o of § 2 and hence, for this
degree of accuracy must be not less than 10% Now it is clear
that 10* observations cannot be made by any process of looking
at the instrument and writing the observation down on paper:
on a favourable estimate the process would need a month's
continuous observation, day and night. Accordingly we must
start our discussion of what instruments are to be used with
considering how this large number of observations is to be taken.
§9. The obvious method of taking this large number of
observations is to record photographically the fluctuations of the
instrument and to deduce the value of 6%7 from the resulting
T
trace by finding the value of : i 6? rdt. It would not be hard
0
to devise a mechanical integrator which would give the value of
| y’d« for any irregular curve, and, if this instrument were sensitive,
its indications would correspond to an average taken over a very
large number of cases: in fact, if dx is the smallest interval over
which the instrument can be expected to distinguish between
different values of y, then an integration over a length # would
Mr Campbell, The study of discontinuous phenomena. 127
be equivalent to ~ observations. But it might appear at first
da
sight that this method was unjustifiable because all the periods
fT would not be independent. But the only dependence between
them is expressed by
SS OS cha Ga) A) Pee onal 7) eee (22),
a relation which affects in no way the argument that the probable
value of },(7,) is independent of 7): it is independent of everything
except Wr and, as was shown in § 3, N7 is independent of the
way 7 is selected. Or, if that proof seems inconclusive, we may
remember that the average value of 0” 7 for successive independent
periods 7 must be the same at whatever moment (distant by an
amount greater than 7’ from the moment of insulation) the first
period is dated. ‘The proposed method consists of nothing more
than averaging the averages of the same number of independent
periods starting from different moments.
Again, it may be argued that this method adds nothing in
accuracy since the same observations are used over and over
again. It is quite true that the method does nothing to diminish
errors due to faulty observations of 0’p, but 1t does diminish errors
due to the application of a theory in which we have assumed
y= oo to experiments in which > is finite.
We may note also that photography adds to the accuracy
in the observation of the position of a moving object. The only
objection to the method is that greater weight is assigned to
observations in the middle of a series than to those at the ends,
but this objection does not seem to be serious; if observations are
really of equal weight no harm is done by attributing a greater
weight to a selection taken at random.
10. Let us now consider the instraments which it will be
desirable to use.
Firstly, we must be able to determine their constants with
accuracy. The determination will doubtless be carried out by
raising the electrode system (including the resistance) to a known
potential v and watching the return of the needle to zero. (See
§ 16, below.) The equation of motion of the needle in this
experiment will be
G/—bAne gal ae er bl te) Pen RUN aa mn wees (23).
where a, 2, p are as before and
oe oe
(Ip’ — up + k) a—B
Re _e(@ap)= Ve
a—p
128 Mr Campbell, The study of discontinuous phenomena.
If the quantities a, 8, p are all different, it will be no easy
matter to find their separate values: the analysis of a curve into
three component exponentials involves great labour and the result
is not likely to attain a high degree of accuracy. But most
electrometers and electroscopes are either just periodic or just
aperiodic, and they can be adjusted to the boundary condition
between these two states without great difficulty. But in this
boundary state
Vw—4/k=0 and a=.
Let us suppose, then, that @ =a+ +, where y is small compared
to a. ‘Taking into account the values of the constants, A, B, A’, B’,
our equations undergo the following simplifications. (23) becomes
OG =(Via Per Pet = ot Bet... nanan (23’),
J (é) (equation (6)) reduces to
f[O=H=2 6" Se) = yibot se ee (6’),
and (21) becomes
1 1 2 age
1 Pecos, ee ea ae
A pe ee eee
SE ae
From (6’) and (21’) it is evident that nearly equal values
of p and a are to be avoided: for, if these two quantities are
equal, the two equations contain only terms involving the small
quantity y, which is hard to determine. Accordingly we must
make one of the two quantities p and a very large and the other
very small. There are three reasons why a should be made large
and p small.
(1) A small value of p corresponds to a high value of the
resistance of the Bronson cell. But the greater this resistance,
the greater is the deflection of the indicating instrument for a
given current passing through the cell. Since it is easier to
measure variations of the same proportional amount in a quantity,
when that quantity is large, than when it is small, it is desirable
that the steady deflection of the indicator, corresponding to the
mean current, should be as great as possible.
(2) A large value of « makes the terms involving the
unknown small quantity y negligible. Any slight deviation from
the boundary state between periodicity and aperiodicity will be
unimportant.
(3) If a is large the required constants can be determined
more easily from the equation (23’). Since p and @ are very
different, the value of the terms involving e~™ can be found from
Mr Campbell, The study of discontinuous phenomena. 129
the beginning or end of the observed decay curve, and those
involving e~? from the end or beginning, according as a is greater
or less than p. If a is large, ¢ will be small for the part of the
curve over which a is determined, and the term in y will be of
very little importance.
All the considerations advanced indicate that a Bronson cell
should be chosen with as high a resistance as possible, and an
indicating instrument with as short a period as possible. It
seems desirable, therefore, to employ a gold-leaf or quartz-fibre
electroscope in place of a Dolezalek electrometer. The only
objection to the use of such an instrument is that it will be
somewhat difficult to determine with accuracy the value of its
time-constant =, which will be of the order of one second. But
it must be remembered that, if a is large compared to p, the terms
in (21’) involving the former quantity are small compared to those
involving the latter. Moreover, if the movement of the instrument
is recorded by photography, the value of this quantity may be
found by a method similar to that employed for measuring the
constants of an Hinthoven string galvanometer. The use of a
Dolezalek electrometer seems prohibited, since, if it is aperiodic,
its time-constaut will be so great that it will be difficult to make
the Bronson resistance so large as to avoid an approximate equality
between a and p.
§11. This elaborate discussion of experimental methods will
be worthless unless there is some reason for believing that the
method is not affected by some inevitable source of inaccuracy.
There seems no reason why the observations should not be taken
with very considerable accuracy, and the theory that has been
given is, so far as I can see, complete and trustworthy. Let us
consider the sources of systematic error which cannot be eliminated
by the most careful experimentalist.
Firstly, there is the Bronson resistance: the current through
this instrument is subject to fluctuations which are added to those
due to the source observed. These fluctuations can be diminished
by using @ rays in place of a rays, as the agent of ionisation in
the resistance: for though a much larger number of § particles
will be required and the absolute error, measured in number of
8 particles, will be increased, the number of ions produced by a
8 particle is so much less than the number produced by an a
particle that the absolute error, measured in current, is less. But,
against the use of 8 particles there is the objection that they
cannot, with any convenience, be absorbed completely in the air
of the resistance and hence chance fluctuations may arise from
changes of temperature, etc. But im any case, the error due to
the resistance can be eliminated by calculating the value of the
130 Mr Campbell, The study of discontinuous phenomena.
mean fluctuations by means of an approximate value of the
electronic charge. (It may be noted that it might be possible
to use some other form of high resistance, but probably all
conductivity is ultimately discontinuous and we know far more
about the conductivity of a gas than about that of a solid or
liquid.)
Secondly, there is a source of error in the fluctuations of other
parts of the apparatus during the period of observation: the cells
used for maintaining the potential are the most likely source of
trouble on this account. Perhaps such errors might be estimated
and eliminated by means of carefully devised ‘blank’ experiments.
Meyer and Regener seem to suggest that an error may be
introduced by the finitude of the time required for a charge
received by the electrode system to attain a steady distribution
on that system. But it can be shown readily by a little arithmetic
that error from this source is negligible. The error could only
enter by fluctuations of the electrometer due to the vibration of
the charge about its final position. Now, if A is the resistance
of the vibrating circuit (in ohms), Z its self-inductance (in henries),
C its capacity (in farads), the period of vibration of the charge is
Aor L,
eS
Vea
Now taking the values of R, L, C, which will give the greatest
possible value for the period, we may put R=1, C=10™%, L=10°
(remembering that the self-inductance in henries of a solenoid
of 100 turns and 1 cm. area is 10~*). Then the period is about
10-8 seconds. Now in the experiments of Geiger and Meyer and
Regener the number of a particles coming off per second was
never greater than 10%: hence the period of oscillation of the
charge is small not only compared with that of the instrument,
but also with the average interval between two charges.
§12. It may be desirable to comment upon the work of
Meyer and Regener in the light of the considerations which
have been advanced.
Meyer and Regener did not make use of the actual theory
which has been elaborated, but they made use of its principle.
They assumed that A? was proportional to 1/N and that the
factor of proportionality depended on the instrumental constants
only: this assumption, as we have seen, is justified. Accordingly
they were justified in their expectation that, if the same instru-
mental arrangements are used throughout, A? should be pro-
portional to 1/N for different values of NV. Since they only took
some 100 observations of A? they could only hope for an agreement
Mr Campbell, The study of discontinuous phenomena. 131
between theory and experiment of about 10°/,, in place of the
1°/, at which we have aimed.
The best series of their results shows such an agreement
as might have been anticipated, but in other series the value
of A? for large values of WV was too large compared with that
for the small values. In the first series an aperiodic electrometer
was used, in the second a periodic instrument. It is not obvious
from the theory that has been given why this distinction should
be found between different experimental arrangements: for the
only difference made in equation (21) is that a and 8 are complex
with a periodic needle and real when the needle is aperiodic.
But Meyer and Regener’s method of observing the fluctuations
is open to exception: they took a reading of 67 only when the
needle reversed its motion at a peak in the fluctuation curve.
Now there is no reason that I can see for choosing the peaks for
observation in preference to any other points on the curve: the
effect of the various particles emitted is integrated by the instru-
ments at the peaks in a manner no less complex than when the
needle is moving constantly in the same direction. The only
justification for choosing the peaks is that they are easy to observe
(since the needle is at rest) and that they are points chosen at
random. Now it seems likely that there might be a tendency to
overlook peaks in the curve near the zero position of the needle,
when the total range of the fluctuation is small, and to observe
all the peaks which are more distant from the zero position.
This tendency would be the more marked, the greater the range
of the fluctuations and the swifter the motion of the needle. For
the latter reason it would be more marked with a periodic instru-
ment than with an aperiodic, and for the former reason it would
be more marked when the total current was large. Accordingly
we might expect to find that, in the case of the periodic needle,
the observed values of A? would be too large in the case of large
values of JV, relatively to those values for smaller values of V. This
differentiation is what is shown in Meyer and Regener’s tables.
On the whole, Meyer and Regener’s attempt to prove the form
of the relation between A? and = seems to have been fairly
satisfactory: but criticism can be directed against their attempt
to deduce from A? an absolute value for = In the first place,
they seem to neglect altogether the effect of the constant of the
Bronson resistance and practically write
132 Mr Campbell, The study of discontinuous phenomena.
If their absolute value accorded well with that deduced from other
work it can only be because p was small compared with a: but,
for all they say, p might have been less than a, or, still worse,
equal to a.
Meyer and Regener also introduce a curious correction by
extrapolation for the capacity of their electrode system. I should
have thought that it was obvious on general grounds that the
value of A? was independent of the capacity as shown by (21), for
both @p and (Or°) are inversely proportional to the capacity.
They extrapolate for zero capacity: but, surely, if the capacity is
zero the fluctuations must be infinite and the value of W infinite.
If extrapolation is to be used at all, it would appear to be more
reasonable to extrapolate for infinite capacity: such a process
reduces the term in p (equation (20)), which they neglect, to zero
—but unfortunately it reduces all other terms in the same ratio.
Lastly, Meyer and Regener, in estimating the average value
of A?, divide SA? by n—1, and not by n, where n is the total
number of observations. There seems to me a confusion here
with the determination of the probable error of a variable given
by a set of dependent equations from the ‘residuals’ of those
equations after the probable value of the variable is substituted.
But there seems to be no quantity analogous to ‘residuals’ in the
case we are considering: the mean fluctuation is simply pro-
portional to the mean ‘error’ in J.
Geiger’s method.
§13. We will now proceed to the discussion of Geiger’s method,
in which no Bronson resistance was used, but the current due
to one a ray source balanced by another current, opposite in sign
and, on the average, equal in modulus, due to another source.
The deflection of the needle is the algebraic sum of the deflections
due to the two sources.
If we consider only one source, the equations corresponding
to (3) and (5), giving the deflection of the needle at all times
after one or m particles respectively have been emitted from that
source, can be found directly from those equations by putting
p=0. Hence, using the same notation as before,
@ Aen Bean! Ae Ph ane eae eee (24),
Ke B me a
where Sp ie Bis mae
and On= pane (Ales i eB emer eae eee eae (25)
=D IG) (ay) hoe: oe eee (26).
Mr Campbell, The study of discontinuous phenomena. 133.
§14. Let the suffix + denote in all cases quantities corre-
sponding to one source, and the suffix — denote quantities corre-
sponding to the other source. Then, it is clear that (10) may be
replaced by
3, (047+ 0-2 =vE)- 1 Pip Pp Zpa7 (H40(7) + b-0(7)) F(rr)P. 20);
where ¢$,,(r) and ¢_,(7) may have any of the possible values
Nr+a4,..-, Nr+ ain, or —Nr+a4,..., -N7+ £4», respectively,
for we must remember that V,=— _.
Reasoning in precisely the same way as before, we arrive at
the following equation corresponding to (13),
Sy (Os0+ Ox) = Day F? (rr) Sho Bp Pp (G47 + Oa) eee (28).
Now 3f7; ©, B_, (#1, +47) is the average value of (#,,— 2+)
for a very large number of values of that quantity. But by a
well-known theorem in probability, the average value of (a + by
is a+? if a and 6 are independent. But the average of 24,7
and of #_,? is the same and equal, by (1), to 2N7. Hence, we get
in place of (15),
t=T
= 3, (O.7+0_7)'=2N | HRSG iowa, ee Ueeeati a (29)
t=0
= ON SE + 55+ Pel + 5 + B +223} 80),
or A? =2N (ul +) (say) ........0- ROIS NT ay le eateeneen (31).
Now, since A” is dependent on 7’, we cannot compare directly
values of A’ for different values of 7. That is to say, if we record
photographically, as suggested in § 10, the values of A® for all
values of 7, we cannot put 2No (average of all these values
of A”). We must compare values of A? for different values of 7
by dividing each value of A”? by the appropriate value of (w7'+ v),
19,
and then take the average of We cannot even, as might
ul +0°
appear at first sight, take the difference of values of A’ for a series
of times differing by 7 and equate the average of the squares of
these differences to 2 (wZ’'+v): for such a procedure would involve
the false proposition that
[A Ay = AF — 0%,
Accordingly the labour of deducing the value of N from the
observed fluctuations will be very much greater than in Meyer
and Regener’s method, for it would be difficult to construct a
134 Mr Campbell, The study of discontinuous phenomena.
mechanical integrator which should give the value of i Be ci
(ax + b)
for a wholly irregular curve.
§15. As regards the choice of instruments for this method,
the conclusions reached in considering Meyer and Regener’s
method are still valid. Since p is zero there is no need for
considering the relation between the periods of the electrometer
and the resistance, but it is still desirable that a should be very
large. For there is some uncertainty in the determination of the
value of this quantity: since the importance of the terms involving
a in comparison with the term PT, which does not involve a,
decreases as a increases, it is clearly desirable to make a as large
as possible, that is, to use an electroscope with as short a period
as possible.
On general grounds Geiger’s method seems less satisfactory
than that of Meyer and Regener for observations on phenomena
for which both methods are, in principle, equally applicable. But
it is easy to imagine circumstances in which Geiger’s method
would, and Meyer and Regener’s would not, be applicable: for
instance, the object of the experiment might be to detect dis-
continuity in the difference between two sources, and indeed
I am engaged at present in endeavouring to conduct such
experiments. It is desirable, therefore, to consider Geiger’s
method a little more closely.
§16. It must be pointed out that the theory of Geiger’s
method which has just been elaborated does not represent any
practicable experimental conditions. It is impossible to reduce
the quantity p accurately to zero. In the first place, there is
always an ‘insulation leak, which acts like a Bronson resistance
and sets a limit to the deflection which the indicating instrument
will attain when acted upon for an infinite time by a finite current.
But this leak can (though with great difficulty) be made so small
that values of 7’ can be chosen such that a7’ is very large and
pT is very small. In such a case Geiger’s method could be applied
according to the theory just given. But, in most of the cases to
which the method is likely to be applied, there is also an ‘ apparent
insulation leak, which is a far more serious matter. It must
be remembered that no ionisation current is really perfectly
‘saturated.’ A condition can often be attained in which an
increase of the acting potential difference from 1000 to 2000 volts
does not increase the current by more than 0-001 of its value, but
this does not prove that an increase of 1 volt in the P.D. may not
cause an increase of one millionth in the current. And a change
of one millionth may be extremely important when we are
concerned with the minute differences in the magnitudes of two
Mr Campbell, The study of discontinuous phenomena. 185
balanced currents very nearly equal. The effect of a lack of
perfect saturation is to diminish the current due to either source
when the potential of the electrode is of the sign corresponding
to a preponderance of the current due to that source: it sets a
finite limit to the potential which the electrode can attain,
diminishes the magnitude of the fluctuations and, in every manner,
acts like an insulation leak.
Errors from this source, even if their possibility had occurred
to me, would have been rejected as unimportant, if I had not had
actual experience of them. I have found the false insulation leak
a very serious trouble in dealing with currents for which saturation
is likely to be far easier of attaiment than im the case of a ray
currents; these currents are those due to the photoelectric effect
in a very high vacuum. In dealing with these currents, the
saturation, tested by the ordinary method, is perfect at 50 volts:
tested by balancing two currents and then watching the decay
- of a potential difference applied to the common electrode, saturation
is not perfect even with a P.D. of 500 volts, though it is much
more nearly perfect than at 50 volts.
The existence of this false insulation current leak reduces
Geiger’s method to that of Meyer and Regener. p has a finite
value which can be found by watching the decay of a P.D. given
to the electrode when the two currents are balanced. It should
be pointed out that this apparent insulation leak affects Meyer
and Regener’s experiments also: in that case too the value of p
must be found when the current to be measured is flowing through
the Bronson resistance and the compensating P.D. applied.
17. A few remarks on Geiger’s work are all that remains.
(1) In the first place we may note that by taking some
100 observations only of the fluctuations Geiger, like Meyer and
Regener, introduced a probable error of some 10°/,. Since the
agreement which he found between theory and experiment was
of this order of accuracy, it might seem that in other respects
his work was satisfactory. But
(2) It seems to me that Geiger employed a totally inadequate
and inaccurate theory in the interpretation of his observations.
He assumes, like Meyer and Regener, that the value of his
fluctuations depends only on the constants of his instruments,
but equation (33) shows that it is also a function of the time
of observation. Only the most general consideration is necessary
to show that in Geiger’s method (assuming the absence of an
important insulation leak) the effects of the particles which came
off at a distant time are as important as the effects of those which
came off only just before the moment of observation: the mean
value of the fluctuations over any short period must depend upon
the distance of this period from the time when the electrode was
VOL. XV. PT. II. 10
136 Mr Campbell, The study of discontinuous phenomena.
insulated. But Geiger adds all his fluctuations together, whatever
the time of observation, as if they were comparable.
Accordingly it appears to me that Geiger’s expectation of
obtaining a result even in approximate accordance with - that
predicted by other work was justified only if he had a large
false insulation leak.’ If there is such a leak, then Geiger’s
method is reduced to that of Meyer and Regener, and all observa-
tions at more than a certain distance from the moment of
insulation are comparable. The existence of an insulation leak
would also explain that the ‘time of swing of the needle’ (53 secs.)
is so much smaller than that which is found with most Dolezalek
electrometers: for the period between two peaks might then
depend, not on the vibrations of the needle, but on the period
of decay of his quasi-‘ Bronson-resistance. But, if this suggestion
is correct, he neglected totally the real time of swing of his needle.
(8) As a minor point we may note that Geiger, attempting
to use von Sie theory, puts ae Correctly
| A’| = woe — for one source of rays and 2 Pee — for 2 inde-
pendent sources (error about 20°/,). The quantity which should
be equal to VN is J/&®, As I have pointed out, it seems
impossible to find a complete expression for the value of | A’|
in terms of NV and the instrumental constants.
In view of these sources of error, it is difficult to avoid the
conclusion that the close agreement found by Geiger between
prediction and experiment was mainly fortuitous.
In conclusion I must offer my best thanks to Mr G. H. Hardy
for his invaluable help in §§ 5—8: the main principle of the
argument is his rather than mine; to Sir J. J. Thomson, who
has pointed out several errors in the original calculations; and
also to Mr T. H. Laby, whose acute criticism first turned my
attention to the subject and aided greatly in the attainment of
clear ideas.
Summary.
§ 1—3. A slight modification and generalisation of von
Schweidler’s theory of the fluctuations in the emission of rays
by a radioactive substance.
§§ 4—7. A consideration of the theory of Meyer and Regener’s ©
experiment based on von Schweidler’s work.
§§ 8-—12. Application of this theory to experimental arrange-
ments.
§§ 13—17. The theory of Geiger’s experiment in the same
direction.
Miss Wheldale, On the nature of anthocyanin. Tair
On the nature of anthocyanin. By Miss M. WHELDALE,
Newnham College. (Communicated by Professor Bateson, F.R.S.)
[Read 8 March 1909. |
Many investigators have suggested, from time to time, that
a relationship exists between the widely distributed tannins in
plants and the equally widely distributed pigment known as
“anthocyanin.” CURTEL', DENNERT?, GAUTIER*, ICHIMURA‘,
MIRANDE*, NEWBIGIN®, WIESNER’, WIGAND® and ZOpF®, among
others, mention the occurrence of a colourless chromogen, of the
nature of a tannin, in tissues, which eventually may become
coloured with anthocyanin; the colouration- arises under the
influence of various agents, such as nutrition, temperature, light,
and injury, either mechanical or such as is brought about by
attacks of fungi, etc. The process of transition, moreover, from
chromogen to pigment has been regarded as one of oxidation.
Not only has the above relationship been established, but the
view has also been held that anthocyanin itself is some compound
of a tannic acid.
OVERTON™, for instance, from the increased production of
anthocyanin brought about by artificial feeding of plants with
carbohydrates, arrived at the conclusion that this pigment may
very possibly be a sugar compound of a tannic acid, that is a
glucoside.
GAUTIER" also isolated various colouring matters from the
red leaves of the Vine and he regards these pigments as coloured
tannic acids.
PFEFFER”, in a general review of the subject, states that the
red and blue pigments dissolved in the cell-sap, such as anthocyanin,
seem to be tannins or compounds allied to phenols, though in his
view they may also be derived from other substances since they
often occur in plants which contain no tannin.
HEIsE®, in addition, isolated two pigments from the Bilberry
and showed one to be the glucoside of the other. Both substances
appear to be aromatic compounds though they have not directly
been proved to be tannins.
The word tannin is a somewhat difficult term to define;
it is used in general for a class of substances very widely
distributed in plants and having certain properties in common.
10—2
138 Miss Wheldale, On the nature of anthocyanin.
Their characteristics, as given in most text-books, are an astringent
taste, the production of a blue or a green colour with iron salts,
tanning properties with animal membranes, power to precipitate
albumin and gelatine, etc., etc. The exact constitution of the
tannins is also rather indefinite though it is obvious that they are
aromatic compounds of the benzene series. Broadly speaking
tannins include numerous tannic acids, such as gallic, gallotannic,
catechinic, caffeic, protocatechuic, diprotocatechuic, ellagic, quer-
citannic, etc., usually existing in plants in the form of glucosides,
z.e. ethereal compounds with various sugars or with the trihydric
phenol, phloroglucin.
It has been suggested that tannins may be divisible into
two groups, derived respectively from a dihydric phenol, such
as pyrocatechol, and a trihydric phenol, such as pyrogallol. The
kind of relationship might be illustrated as follows :—
CeH4(OH), CsH3(0H),. COOH CgH3(0H),.CO.0.CgH;.O0H. COOH
pyrocatechol protocatechuie acid diprotocatechuic acid
CgH3(OH)s CgH.(OH)3. COOH CgH2(OH)3.CO.0.CgH2(OH)2. COOH
pyrogallol gallic acid tannic acid or digallic acid
The tannins included in the first group give as a rule an
iron-greening reaction (though this is by no means invariably
the case), produce pyrocatechol on dry distillation and proto-
catechuic acid when fused with caustic alkali. Those of the
second group give an iron-blueing reaction, produce pyrogallol
on dry distillation and gallic acid on fusion with caustic alkali.
WaacE™ and also NICKEL” are of the opinion that another
series of tannic acids arises from the oxidation of phloroglucin,
the isomer of pyrogallol :—
CgH3(0H)s CeH2(0H); . COOH CsH.(OH)3. CO. 0. CgH2(OH),.COOH
phloroglucin phloroglucin carbonsaure phloroglucin gerbsaure
(carboxylic acid) (tannic acid)
Hence there may well be a complexity of tannins of different
natures.
With a view to finding out whether, and if so, in what way
anthocyanin is related to tannin, the extracts from flowers of
numerous natural orders, both with and without anthocyanin,
were tested for tannin with various reagents. Although the
behaviour of the pigments has been diverse in many ways,
a certain amount of classification can be based on the results
obtained.
It must at the same time be borne in mind that some of
the reagents used in these tests, react not only with the tannins
but also with many other bodies, such as phenols and their
numerous derivatives.
Miss Wheldale, On the nature of anthocyanin. 139
The reagents* employed were as follows :—
(1) Strong bases, such as solutions of caustic potash or soda
and of ammonia.
(2) Lime water. A blue, brown or red colour or precipitate
shows tannins.
(3) Strong acids, such as sulphuric, hydrochloric and nitric
acids. The reactions of BRISSEMORET" are interesting in this
connection though they have not been employed to any great
extent.
(4) Iron salts. Ferric chloride solution was used and also
a solution of ferrous sulphate, in which some oxidation to the
ferric salt has taken place. A blue-black or dull green colouration
shows tannins.
(5) Precipitation by basic lead acetate which precipitates
most tannins and glucosides.
(6) Potassium ferricyanide solution and ammonia. A reddish-
brown colouration changing to brown shows tannins.
(7) Uranium acetate solution. A brown precipitate or
reddish-brown or brown colour shows tannins.
(8) Ammonium molybdate solution, both alone and with the
addition of a saturated solution of ammonium chloride. According
to Gardiner+ alkaline molybdate gives a red colour with tannin.
If excess of ammonium chloride is added, a voluminous yellow
precipitate is produced. Moreover by means of this reagent,
according to the above author, tannin may be readily separated
from tannic, 2.¢. digallic acid, for whereas the compound of tannin
and molybdate (?) is insoluble in ammonium chloride, that with
tannic acid is soluble. The reagent therefore separates the
glucoside tannins from tannic acid.
As a preliminary statement it may be said that tannins, like
that of the oak gall, giving an intense blue-black colour with iron
salts and also reactions 2, 6, and 7 are rare among herbaceous
plants. There are however widely distributed among the latter,
certain colourless or slightly yellow substances, giving an iron-
greening reaction though they are not typically tannins, since
they do not as a rule give reactions 2,6, 7,and 8. These substances
are characterised in addition by the bright yellow colour produced
when they are acted upon by strong bases and by lime-water.
They give the same colour also with strong mineral acids, such
as sulphuric and hydrochloric, and they are precipitated by basic
lead acetate as canary-yellow precipitates.
These reactions are best seen when extracts of white flowers
are used or those of yellow flowers, in which the colour is due
to plastid pigment only. Flowers giving these reactions are
arranged in the following scheme.
* Darwin and Acton, Physiology of Plants. + Gardiner 1’,
140 Miss Wheldale, On the nature of anthocyanin.
I. White flowers, of which an extract gives a bright yellow
colour with alkalis and acids, a bright yellow precipitate with
basic lead acetate and a reaction with iron salts.
(a) Those giving a green colouration with iron salts:
Mesembryanthemum Haworthii, Colchicum sp., Nerine flexuosa,
paper white variety of the polyanthus Narcissus, white berries
of Symphoricarpus racemosus, white variety of Chrysanthemum
carinatum, white variety of autumnal cultivated Chrysanthemum,
ivory white variety of Viola tricolor, white variety of <Abutilon
striatum, Hrica Bowieana and white variety of Primula sinensis.
(6) Those giving a blue colouration with iron salts: None.
II. Yellow flowers (albino as regards anthocyanin, but with
yellow plastid pigments), of which the extract gives the same
reactions as those in I.
(a) Those giving a green colouration with iron salts:
Ivory variety of Hehanthemum vulgare, Calendula officinalis,
yellow variety of autumnal cultivated Chrysanthemum, Erigeron
Canadensis, Garllardia sp., Gazama splendens, Helenium nudiflorum,
Helianthus annuus, Pieris pauciflorus, Senecio Jacobaea, pale and
deep yellow varieties of Zinnia elegans, Hypericum Hookerianum,
Spartium junceum, Linum flavum, Bartonia aurea, yellow variety
of Abutilon striatum, Jasminum nudiflorum, Argemone grandiflora,
Eschscholtzia Californica, Primula Kewensis, Potentilla fruticosa,
Hyoscyamus chloranthus, yellow variety of Salpiglossis grandiflora,
calyx of Physalis alkekengi, pale and deep yellow varieties of
Tropaeolum majus, Tropaeolum canariense, and pale and deep
yellow varieties of Viola tricolor.
(b) Those giving a blue colouration with iron salts:
Alyssum maritimum.
Exceptions were the following, which give a yellow precipitate
with basic lead acetate, a yellow colour with alkalis but not the
above reactions with iron salts: Taraxacum officinale*, Brassica
sinapis*, Cucurbita Pepo*, and fruit of Lycopersicum esculentum.
It might be noted that these exceptions are chiefly plants
which do not normally produce anthocyanin.
The xantheic pigments of many yellow flowers seem to be
very similar in nature to the substances present in the above
Classes I. and II. They differ in that the yellow extract usually
deepens to orange-yellow or red with alkalis and acids and the
precipitates with basic lead acetate are of corresponding shades.
The iron reaction is usually green. Class III. contains genera
whose flowers give these reactions.
* Tested only with ferric chloride which does not always give a satisfactory
result.
Miss Wheldale, On the nature of anthocyanin. 141
III. Yellow flowers containing a so-called xantheic pigment
(sometimes in addition a yellow plastid pigment), of which the
extract gives a colouration with iron salts; a yellow, orange-yellow,
orange or red precipitate with basic lead acetate and similar
colourations with acids and alkalis.
(a) Those giving a green colouration with iron salts:
Mesembryanthemum pomeridianum (yellow)*, Centaurea eriophora
(orange-yellow), Centawrea scabiosa (orange-yellow), yellow variety
of Chrysanthemum carinatum (orange), Corydalis lutea (orange-
yellow), yellow variety of Dahha variabilis (red), yellow variety
of Helichrysum bracteatwm (orange), Tagetes signata (orange),
Coromlla glauca (orange), Mirabilis Jalapa (yellow), Primula
acaulis (orange), Calceolaria sp. (orange), and Nemesia strumosa
(yellow).
(6b) Those giving a blue colouration with iron salts:
LIinaria multipunctata (orange-red) and Linaria vulgaris (orange-
red). The following are exceptions in that they do not give the
above reactions with iron salts: Coreopsis Drummonditt (red) and
Verbascum Lychinitis (yellow).
When anthocyanin was present in the genera examined, the
reactions given by the usual reagents were diverse, but the more
common type of reaction is that given in Class IV., 1.e. a green
colouration with alkalis, a green precipitate with basic lead acetate
and a green or blue colouration with iron salts. It is doubtful
whether the blue colouration given by the anthocyanin of many
herbaceous genera is in any way similar to the true iron-blueing
tannin reaction. Extracts from the flowers of some shrubs, such
as red varieties of Rosa, give a true iron-blueing reaction like that
of the oak-gall, and this result may be due to admixture of tannin
present in the plant. Iam inclined to believe that the iron-blueing
reaction of the flower extract of herbaceous plants may only be
a specific reaction of anthocyanin itself and not an indication
of a true tannin nature of this substance. Yet this point of view
by no means vitiates the suggestion that this pigment may be an-
aromatic substance closely allied to the tannins.
The anthocyanin of Class IV. is of the purple or purplish-red
type. Though the colours of the flowers, from which it is obtained,
often differ among themselves, the alcoholic extracts have the
common property of being purple or purplish-red in colour.
IV. Red, purple or blue flowers containing anthocyanin
(sometimes in addition plastid pigment), of which the extract
gives a green colour with alkalis and a green precipitate with
basic lead acetate.
* Denotes colour given with alkalis and basic lead acetate.
+ Tested only with ferric chloride.
142 Miss Wheldale, On the nature of anthocyanin.
(a) Those giving a green colouration with iron salts:
Blue Vinca major and blue Campanula” sp., carmine pericarp
of Huonymus europaeus, blue Tradescantia virginiana, blue Aster
tripolium, blue and magenta varieties of Cineraria sp., crimson,
mauve, and purple varieties of autumn Chrysanthemum, crimson
Mieracium rubrum, magenta variety of Helichrysum bracteatum,
pink and scarlet varieties of Zinnia elegans, mauve Aubrietia
graeca, brown Cheiranthus Cheiri, pink H’pacris pulchella, carmine
Salvia dulcis, purple Salvia Horminum, purplish-red Salvia
involucrata, blue Anemone coronaria, carmine Tropaeolum speci-
osum, purple varieties of Viola tricolor.
(6) Those giving a blue colouration with iron salts:
Orange Alstroemeria aurantiaca, magenta Impatiens episcopr,
erimson Helianthemum vulgare, pink Hcheveria retusa, magenta
Azalea amoena, floral bracts of Huphorbia splendens, carmine
leaf bracts of Huphorbia pulcherrima, crimson Coronilla viminalas,
orange Laliwm Trgrinum, crimson <Abutilon striatum, purple
Fuchsia sp. black berries of Rosa pimpinellifolia, black berries
of Atropa Belladonna, magenta Petunia violacea.
From the above classification we may conclude that among
herbaceous plants aromatic substances giving an iron-greening
reaction are common. An iron-blueing reaction however is rare
when anthocyanin is absent, but more common when this pigment
is present, though it is probable that the reaction in the latter
case does not indicate a true tannin nature for this substance.
When a species is in type anthocyanic with an albino variety
(as regards this pigment), for example Chrysanthemum, Viola,
Abutilon, Helianthemum, Zinnia and Helichrysum, then with
alkalis the albino extract is coloured yellow and that of the
anthocyanic type blue with a small amount of alkali but green
with excess. Similarly the albino extract gives a yellow precipitate
with basic lead acetate, and that of the type a green precipitate.
The iron reaction is usually the same for both type and variety,
though in the case of Helianthemum and Abutilon, the iron
reaction is green for the non-anthocyanic varieties but blue for
the anthocyanic type.
A possible explanation for the reactions observed might be
as follows:—That many plants free from anthocyanin, and also
albino varieties of anthocyanic types, contain colourless aromatic .
chromogens, probably often in combination with sugars as
glucosides as suggested by OverTON®. These chromogens appear
to have acid properties and usually give an iron-greening reaction;
as present in the plant in the undissociated state they are almost
colourless, but on addition of strong alkali a dissociable salt is
formed, of which the anion is bright yellow. The yellow colour
disappears again on neutralisation with acid, so that the reaction
Miss Wheldale, On the nature of anthocyanin. 143
resembles that of an acid-alkali indicator. With heavy metals,
such as copper and lead, insoluble coloured salts are formed.
There appears to be evidence, as will be discussed later, that
the production of pigment in anthocyanic species is brought about
through the agency of an oxydase so that anthocyanin may be
regarded as a coloured oxidised product of an aromatic chromogen
and moreover, like the unaltered chromogen, as an acid capable
of producing salts. In the acid state the molecule of anthocyanin
is red but the addition of alkali produces a blue salt.
We may suppose that there is usually unaltered chromogen
present in the plant in addition to anthocyanin, and the simul-
taneous existence of these two bodies would account for the green
colour given by alkalis and the green precipitate by basic lead
acetate, 7.e. a mixture due to the blue salt of the oxidised product
and the yellow salt of the chromogen. The stronger—more
oxidised—acid would probably react first with bases; hence the
blue colouration with a slight amount of alkali.
On this supposition, the green precipitates prepared and
analysed by HEISE” and GAUTIER” represents a mixture of the
salts of both anthocyanic acid and its chromogen.
An alternative explanation is that offered by OVERTON™”, who
regards anthocyanin as a di- or poly-basic acid, the blue colour
given by a small amount of alkali being due to the acid salt, the
green colour with excess of alkali to the neutral salt.
GRAFE!, too, is of the opinion that one of the pigments
isolated by him from Althaea rosea is a di-basic acid; he regards
the green colour with alkalis as a specific reaction of anthocyanin
and not one due to admixture with any other substances giving
a yellow reaction.
Evidence for the assumption that the aromatic chromogen
forms a component of anthocyanin has been arrived at through
experiments in cross-breeding*. It appears, from this source,
that the components of anthocyanin can be represented by various
Mendelian factors, the loss of which gives rise to derivative
varieties. In Antirrhinum majus, an ivory-white variety exists,
which is free from anthocyanin, but contains a chromogen such
as those described above. The magenta type contains anthocyanin.
It has been proved experimentally that the factor representing
the chromogen is essential to the constitution of the magenta
type.
Cross-breeding with Antirrhinum shows moreover that the
so-called xantheic pigment of the yellow variety is essential to
the constitution of the ivory-white and is hypostatic to it. In
fact xanthein appears to be a yellow aromatic chromogen in a
* Wheldale 9.
144 Miss Wheldale, On the nature of anthocyanin.
lower stage of formation than the ivory-white, yet capable, like
the latter, of being acted upon by the oxydase with the productions
of anthocyanin, which in this case is mixed with unaltered yellow
chromogen and consequently produces the crimson colour of the
crimson variety.
Antirrhinum is the type of a number of genera in which
the colourless chromogen of the ivory-white variety gives rise,
probably through loss of some factor, to a xantheic pigment.
Definite knowledge as to the nature and constitution of these
aromatic chromogens, from the oxidation of which anthocyanin
may arise, is a difficult chemical problem. I am inclined to
believe that they belong to the flavone and xanthone classes
of natural colouring matters*, which they closely resemble in
properties and reactions. The flavones and xanthones are chiefly
present in plants as glucosides or rhamnosides, most have fifteen
carbon atoms in their empirical formulae and on fusion with
caustic alkali many give protocatechuic acid and phloroglucin.
The nucleus of these substances is y-pyrone, which may be
regarded as an anhydride of a diolefine-dioxyketone :—
Xanthones and flavones are derived from pheno-y-pyrone :—
O
cH
co
Xanthone being a dibenzopyrone :—
O
CO
* See Czapek, Biochemie der Pflanzen.
Miss Wheldale, On the nature of anthocyanin. 145
and flavone a 8-phenyl-benzo-y-pyrone:—
O
CO
Among those of other investigators, the very valuable researches
of PERKIN=— and his colleagues on the yellow colouring matters
of plants in connection with their dyeing properties, have thrown
much light on the constitution of these bodies, and since they are
of great importance in connection with this point I propose giving
a short account of the properties and constitution of the chief
members of the group, as well as their distribution among various
natural orders. The xanthones appear to be less widely distributed
than the flavones and it is to the latter that most importance
may be attached.
Most of the colouring matters may be regarded as arising
from a hydroxy-derivative of flavone :—
O
C-C,H,
C-:0H
co
Generally speaking they are yellow crystalline bodies, not very
soluble in water in the free state, more soluble probably as
glucosides. They are soluble in acids giving yellow, orange or
red solutions, and in the absence of water many form crystalline
compounds with a molecule of the acid, these same compounds
being again decomposed into acid and colouring matter on addition
of water. At the same time they appear to have basic properties;
in alkalis they are soluble, giving again yellow, orange or red
solutions. Many, moreover, are able, in the absence of water,
to withdraw potassium from potassium acetate, with the formation
of a mono-potassium salt. They are precipitated by lead acetate
as yellow, orange or red precipitates and with ferric chloride
solution they usually give a dull green colouration, occasionally
reddish-brown. The decomposition products on fusion with alkali
are frequently phloroglucin and protocatechuic acid, though some-
times resorcinol, resorcylic or hydroxybenzoic acids are formed
146 Miss Wheldale, On the nature of anthocyanin.
according to variations in the constitution of the colouring matter.
With aniline or toluidine nitrate and potassium nitrite they give
a cinnabar-red precipitate. In the plant the flavones mostly occur
as glucosides, the sugar being rhamnose or glucose.
Quercetin C,;H,O; is very widely distributed. It may be
regarded as a pentahydroxy flavone :—
O
OH
OH OH
OH
OH CO
Quercetin occurs free, that is not as a glucoside, in many plants.
The following are interesting examples :—its occurrence in flowers
of Prunus spinosa, Crataegus oxyacantha, Delphinium Zalrl, and
Cheiranthus Chewri; in leaves of Rhus rhodanthema, R. metopium,
Ailanthus glandulosa, Coriaria myrtifolia, Calluna vulgaris; it
exists also in the outer bulb scales of Allicwm cepa and in many
other plants.
On fusion with caustic alkali, quercetin gives protocatechuic
acid and phloroglucin derived from the catechol and phloroglucinol
nuclei respectively.
In many plants on the other hand it is combined with glucose
or rhamnose as glucosides. It occurs as ‘osyritrin’; a glucose
glucoside, in leaves of Osyris compressa; ‘osyritrin’ is also identical
with the ‘wola quercitrin’ of flowers of Viola tricolor variensis and
with ‘myrticolorin’ in leaves of Hucalyptus macrorhyncha. Again
with one molecule of rhamnose it occurs as the glucoside ‘quer-
citrin’ in the bark of Quercus tinctoria and with two molecules of
rhamnose as ‘rutin’ in Ruta graveolens. The flowers of Viola
odorata and Trifolium repens also contain quercetin in the form
of a glucoside.
Morin, C,;H,,0,, occurring in the wood of Morus tinctoria and
Artocarpus integrifolia, may be regarded as an isomer of quercetin
containiny the resorcinol instead of the catechol nucleus :—
0 OH
OH OH
OH
OH CO
On fusion with alkali it gives @-resorcylic acid and phloroglucin.
Miss Wheldale, On the nature of anthocyanin. 147
Rhamnetin, C,,H,,0,, a monomethyl ether of quercetin is found
as a rhamnose glucoside—‘xanthorhamnin’ *—in fruits of Rhamnus
spp. Its constitution may be represented as :—
co OH
OH OH
OCH,
OH O
Isorhamnetin, C,,H,,0;, an isomerous monomethy] ether, occurs in
the flowers of Chetranthus cheiri and of Delphiniwm Zalil: it may
be represented as :—
0
OCH,
On OH
OH
OH CO
Rhamnazin, C,,7H,,0,, a dimethyl ether of quercetin, occurs as a
glucoside in addition to xanthorhamnin in the fruits of Rhamnus
spp.; it may be represented as :—
)
OH isle Oe
OCH,
OH CO
Fisetin, C,;H,,Os, occurs in the wood of Rhus cotinus, R. coriaria
and RR. rhodanthema.
It differs from quercetin in containing a resorcinol instead of
a phloroglucinol nucleus and may be regarded as a tetrahydroxy
flavone :—
Hence on fusion with caustic alkali, the decomposition products
are protocatechuic acid and resorcinol.
* Cp. ‘On some points in the Histology and Physiology of the Fruits and Seeds
of Rhamnus.”” H. Marshall-Ward and J, Dunlop, Ann. Bot. Vol. 1. 1887-8,
148 Miss Wheldale, On the nature of anthocyanin.
Luteolin, C,;H,O,, is found in Reseda luteola and Genista
tenctoria. It is an isomer of fisetin and may be represented as :—
0
OH
OH OH
SNS
OH CO
On fusion with alkali, phloroglucin and protocatechuic acid are
formed.
Myricetin, C,H Os, 1 is found in the bark of Myrica nagt, in the
leaves of Rhus conaria and R. cotinus, R. metopiwm, Pistacia
lentiscus and others. It may be regarded as a hydroxyquercetin
containing a pyrogallol instead of a catechol nucleus :—
g OH
OH on
OH
OH
OH CO
Hence on fusion with caustic alkali it gives gallic acid and
phloroglucin.
Chrysin, C,;HyO,, 1s found in buds of Populus sp. It is a
dihydroxy flavone :—
O
OH
OH CO
Apigenin, C,;H,,0,, occurs in the form of a glucoside—‘apiin’—
in the leaves, stem and fruit of Parsley, Apium petroseliun. It
may be regarded as a hydroxychrysin or trihydroxy flavone :—-
O
OH
OH
OH CO
On fusion with caustic alkali, the decomposition products _ are
phloroglucin and parahydroxybenzoic acid,
Miss Wheldale, On the nature of anthocyanin. 149
Kampherol, C,;H,,O,, occurs as a rhamnose glucoside ‘robinin’
in the flowers of Robinia pseudacacia, and also as another glucoside
in the flowers of Delphinium consolida and Prunus spinosa. It
may be regarded as a connecting link between apigenin and
quercetin :—
(0) OH 0 :
OH OH OH OH
OH OH
OH CO OH CO
Quercetin Kampherol
O
OH SH
OH co
Apigenin
On fusion with caustic alkali it gives parahydroxybenzoie acid
and phloroglucin.
The above account conveys some idea of the wide distribution
of the flavone series of colouring matters. Some fifty to sixty
genera have been examined by PERKIN and his colleagues and
these genera are members of many different natural orders.
Several of the flavones are common to genera by no means
closely allied and again others, as far as his investigations have
gone, are apparently specific. The constitution of these bodies,
as given above, shows that there is great scope for slight variations
and many isomeric forms may exist and may be specitic for different
vlants. At the same time the general nature and tendencies of
these bodies are similar, and it is not difficult to conceive of their
acting as chromogens in the formation of the various kinds of red
pigments found in plants.
I have repeated the method of extraction of PERKIN and
HumMEL” for quercetin from onion skins and I find this body
very similar in its properties and reactions to the aromatic
chromogens present in flowers. Sometimes these bodies crystallise
out from the flower extract asin Narcissus Tazetta*, E'schscholtzia,
and Violat in which case the substance is more easily prepared
in its pure state. The yellow crystalline pigment of Viola is
without doubt the ‘viola quercitrin’ of PERKIN.
* Bidgood #1, + Wheldale 2,
150 Miss Wheldale, On the nature of anthocyanin.
The flowers of the original type in Narcissus Tazetta owe
their colour to the presence of several pigments; the lemon
yellow of the perianth segments is due to plastids containing
xanthin, and the orange yellow of the corona to plastids containing
both xanthin and carotin. In addition, all parts of the flower
contain a yellow flavone pigment which crystallises from the
extract in clusters of yellow needles. To ascertain something
of its nature, this yellow crystalline pigment was fused with
caustic alkali, the melt dissolved in water, neutralised and
precipitated with basic lead acetate. The precipitate on de-
composition with sulphuretted hydrogen and extraction with
ether, gave a crystalline body having the properties of proto-
catechuic acid. The ether extract also gave evidence of the
presence of phloroglucin. Hence there is little doubt that the
Narcissus pigment may be placed in the flavone series.
A white variety of the same Narcissus has no plastid pigments
but a pale yellow non-crystallisable flavone having the usual
characteristics. On fusion with caustic alkali, phloroglucin and
parahydroxybenzoic(?) acid were detected as decomposition
products. Hence the flavone of the variety must differ in
constitution slightly from the crystallme flavone of the type.
A second variety has the crystallisable flavone only in the
perianth, while the corona contains carotin.
A third variety contains a non-crystallisable flavone and
xanthin in addition in the corona.
In a similar way the non-crystallisable chromogen from the
white flowers of Primula stellata and P. sinensis was isolated
and fused with alkali. The ether extract contained phloroglucin
and another body, very probably parahydroxybenzoic acid, since
it gave a red precipitate with aqueous iodine and caustic potash,
which became yellow on addition of acid.
The work of NAyYLor and CHAPPEL” on Rosa gallica forms
an additional confirmation of the above suggestion as to the
nature of the aromatic chromogens. These authors isolated from
the petals of the above species of Rosa a yellow crystalline colouring
matter, giving an orange-red precipitate with lead acetate and
a brownish-black colouration with ferric chloride. ¢It was soluble
in caustic potash to a yellow or orange brown solution and in
sulphuric acid to an orange-yellow liquid.
Fused with caustic potash it gave phloroglucin and proto-
eatechuic acid.
HEISE” also found protocatechuic acid as a decomposition
product from the fusion with alkali of one of the anthocyanic
pigments isolated by him from the Bilberry.
If the existence of a colourless chromogen as a precursor of
‘anthocyanin’ be accepted, it is possible that the recent work
Miss Wheldale, On the nature of anthocyanin. 151
of PALLADIN® may throw light upon the method of production
of the pigment from its chromogen. The above author maintains,
on the evidence of BERTRAND“, that oxydases can only oxidise
aromatic compounds of a certain constitution, and since the
products of oxidation may be coloured PALLADIN terms such
oxydases ‘pigment-building.” He further maintains that chromo-
gens are present in many plants; for he found that if the
extracted sap of such plants be heated sufficiently to destroy
the enzymes existing in the plants themselves, then the addition
to the extracted sap of a small quantity of the peroxydase of
Cuopat and Bacn**"** together with a few drops of hydrogen
peroxide, produces a purple, red or reddish-brown colouration.
As to the constitution of the chromogen, PALLADIN® suggests
that the evidence of OVERTON™ points to the chromogen as being
an aromatic substance combined with sugar and of this nature are
glucosides. To quote PALLADIN:—‘ Die vorstehend beschriebenen |
Versuche und ebenfalls diejenigen OVERTON ergaben, dass
verschiedene Zuckerarten ein Material darstellen, aus welchem
verschiedenartige Atmungschromogene gebildet werden. Auch
Glukoside kénnen wahrscheinlich als Material fiir die Bildung
der Chromogene dienen, wie es auch OVERTON vermutete.
Zugunsten dieser Voraussetzung spricht der Umstand, dass die
meisten pflanzlichen Glukoside Verbindungen verschiedener
Zuckerarten mit aromatischen Stoffen sind: nach den gegenwiartig
bekannten Tatsachen sind auch Atmungschromogene nichts anderes
als aromatische Verbindungen. Die aromatischen Spaltungs-
produkte der Glukoside liefern bei der Oxydation verschiedene
Pigmente. Es ist wohl méglich, dass die bei der enzymatischen
Spaltung der Glukoside in den Pflanzen entstehenden einfacheren
aromatischen Verbindungen direkt als Atmungschromogene
fungieren.”
The peroxydase of CHopaT and BAcH employed by PALLaDIN
is prepared from the root of the horse-radish. Methods of
preparation are given by DE STOECKLIN” and are based upon
the extraction of the ground root with water or dilute alcohol
and subsequent precipitation with absolute alcohol. The ferment
separates out as a white powder, which may be purified by solution
and reprecipitation. The activity of the ferment can be tested by
its power to produce purpurogallin when added to pyrogallol
solution in presence of hydrogen peroxide.
I have prepared the peroxydase by the method of DE SroEcKLIN
and have tested its action upon an extract of flowers of Primula
sinensis. Flowers of a white variety slightly tinged with purple
were gently heated in water and subsequently pounded and filtered.
To the colourless extract a little of the peroxydase solution was
added, together with a few drops of hydrogen peroxide. With
VOL. XV. PT. II. ll
152 Miss Wheldale, On the nature of anthocyanin.
care the formation of a purple pigment can be detected as the
oxydase is added, though it rapidly vanishes leaving a brown
colouration only. The same restoration of the pigment is brought
about sometimes by the addition to the extract of hydrogen
peroxide only, in which case evidently some of the Primula
oxydase is still active. It seems probable that the rapid dis-
appearance of the restored pigment is due to some unfavourable
condition of the experiment.
An attempt to isolate an oxydase from the young flowers
and buds of coloured varieties of Primula sinensis has resulted
only in the production of a solution which gave a brownish-red
colour with pyrogallol in presence of hydrogen peroxide but which
was without effect upon the colourless extract of Primula itself.
Although no positive result has been obtained with Primula
oxydase on its own chromogen, further attempts will be made
to isolate a peroxydase from other genera, such as Antirrhinum,
Lathyrus, etc., and it is possible that these may be more successful.
The theories of PALLADIN and OVERTON however, taken into
consideration with results derived from work in genetics and from
the researches of PERKIN, seem to provide evidence sufficiently
strong to justify the assumption, that anthocyanin is a product
of ferment oxidation of the glucosides of members of the flavone
series of colouring matters, or of substances very closely allied
to these.
If we regard anthocyanin as the product of oxidation of a
colourless aromatic chromogen, then the following table of genera
having many varieties, shows several anomalies :—
In Antirrhinum, Dianthus, Matthiola and Verbena, the
chromogen gives a brown colouration with iron salts, though
the reactions with basic lead acetate, with alkalis and with
acids would indicate that it is of a similar nature to those already
described. In pink—rose dorée—Antirrhinum, red Matthiola,
scarlet Dianthus and scarlet Verbena, the addition of the reddening
factor produces no change in the iron-reaction but only the
ultimate addition of a blueing factor, which then produces a green
iron-reaction—Antirrhinum, Verbena—or a blue iron-reaction—
Matthiola. In pink Dianthus, the reddening factor gives a green,
in other varieties the blueing factor, a blue iron-reaction.
Most frequently, as in Phlox, Lathyrus, Dianthus and Matthiola
(exceptions Antirrhinum and Verbena) as well as in Helianthemum
and Abutilon, the introduction of a blueing factor appears to be
connected with the production of an iron-blueing reaction.
As regards basic lead acetate, the chromogen in Dianthus
and Matthiola does not give the usual reaction, so that the
reds and purples become bluer on addition of this reagent but
no green colour is produced.
weei8 ei weord bee use
uMomq| ~~" oe8 oe weea3 gee :
maorq| °"' : ie aes ystppar
weers Bon users ooo anes
UMOIG eles : me Ystppex oe
umorq| *** ; af a ts ;
umorq| °° ; ; : pox ae
peseyyeun « “ “ poereyyeun *"
anyTq + Lacclehes)
pet Yst) ... * 50 on
“UMOIq weer
umorq| °"" nas re a Cs tie
anyq ° * | weeds ee :
wats Bon a YSst aah ;
Meee a -T19018
uoor13 oe eee Ysippea eee
WMOIG eee sae eee eee eee eychugtn to)
enTq ah goo users Bo ms
uweei8 ia ueeis sgt :
atdind eee eee moors eee eae
wees : “| Ustppet} °"
woeoid op BuO asueIo
ueeis ae Bae asuBio
qInojoo ou} **
TMOIG
10 pax anyq | users || entq | ueers per jasuero
S}[VS WOIT STTeATV
INO) HEYS
oe wmua0is wee . eae sae + eee JOTOT A,
see bareyehest aoe wae sae tae ae nae wee wae JayIVog
: “| Ysippet}| °° pee ; ; “ yurd esol TOURS
‘ds nuagwa4
wee wee13 600 . 5 eee el UISB IN
2 “| ystppet | °~ oy aur * YU eto esoy
ein oe “| Mores || ° ; : AIOAT
F pou an oy 00 a ae 5h MOTIEX
eo peraqteun aba : ‘ ode a : anti AA
snp wnury Luque
ony q OD eee wee tae eee etding
20 pot ° ere . 0: onc 300 Goo
ysintq pe
aad “ poqoayeun °° Sat See at iG “WUBI PUR OFT AA
“ds D10LYy MTT
antq ue es a : : a By twostu119 deoq
ysmyq yoTIVIG
ist “+ | ystppar} a0 : Finan pice ie ie yung
poreyyeun ou an ac wre ot ae MOT[OX
snpphydohuwp snyquoiqg
eee moor3 eee wae eee . eee . . on etding
use138 eae . eee . eee eae eee tee pay
snyouopo snuhyan'T
: weeds eh He ae ej Uesvul ® JOTOTA ‘ MOSUILIO JOSopEys SNOLMIG A
“| ystppet | -" ve oe a0 * quid as01 UOT[BG
nae oe vee osuri0 Jens tee wee . on . AIOAT
see eae OosuvRvIO eee une eae eee tee . AMOTIOX
BBS as 400 — a8 as its a0 io oq AA
tpuomunig vopYy qT
anjq | users pet jadsuero} mojjed
9784908 pBo] OISeq
¢
4)
11—
154 Miss Wheldale, On the nature of anthocyanin.
All forms of anthocyanin so far considered (except the pinks
of Phlox, Dianthus, Antirrhinum, the pink and scarlet of Verbena
and the red of Matthiola) have been of the type which may be
termed purple and purplish-red, that is, though the flower-colours
may be dissimilar, the extracted solution has a purplish tinge and
the colouration with alkalis is green.
The following pink and scarlet colours resemble the red
varieties of Dianthus and Matthiola in giving a red or bluish-red
colouration or precipitate with basic lead acetate and a full green
or some green colour with alkalis :—
Pink Impatiens sultani (violet) *.
» Begonia-Glorie de Lorraine (greenish).
Berries of Berberis vulgaris (unaffected).
Red Delphinium cardinale 7
Scarlet variety of Pentstemon sp. (brownish-red).
From the above examples it is apparent that a difference
in the reactions with iron salts and with basic lead acetate is
frequently associated with the production of an anthocyanin
differently coloured, z.e. pink or scarlet, from the more frequent
purplish-red form.
This difference is even more obvious in the following cases
of scarlet flowers, with the extract of which both alkalis and basic
lead acetate give a red, purplish-red or purple colour:—
Scarlet Impatiens Holstw (reddish)*.
» Lobelia cardinalis (unaffected).
» Salvia splendens (red).
» Phaseolus multiflorus (unaffected).
» Lapaver Rhoeas (brown-red).
» Anagallis grandiflora (red).
» Alonsoa miniata coccinea (unaffected).
These colour differences may be regarded as further evidence
in favour of the suggestion that purple, purplish-red and some
pink forms of anthocyanin are derived from iron-greening chro-
mogens. When the latter are absent from the plant the flower
colour is of a strikingly different shade.
The significance of the change from a green to a blue iron-
reaction, which so often accompanies a blueing of the anthocyanin,
is as yet inexplicable. It is possible that as the oxidation of the
anthocyanin progresses, less of the chromogen remains and hence
the green iron-reaction of the latter is hidden by the iron-reaction
of anthocyanin itself. This suggestion, however, hardly fits such
cases as those in which the chromogen is present in a quantity
sufficient to produce a green colouration with basic lead acetate
and with alkalis, though at the same time the iron-reaction is
blue. Probably examination of a larger number of genera may
* Denotes colour with iron-salts.
Miss Wheldale, On the nature of anthocyanin. 155
throw more light upon this point. In connection with the
statement, that in genera showing various reds and purples,
ie. Phlox, Lathyrus, Dianthus and Matthiola, the ultimate purple
variety contains an anthocyanin giving a blue iron-reaction, it is
of interest to mention the fact that this ultimate purple anthocyanin
can often be differentiated into a redder portion (though not
identical with the anthocyanin of the reds), soluble in alcohol, and
a bluer portion insoluble in alcohol, but readily soluble in water.
All cases have not been thoroughly investigated, but as far
as they go the results point to the conclusion that the bluer
portion gives a blue precipitate with basic lead acetate, a blue
colouration with alkalis, and a blue colour with iron salts.
The bluer portion predominates in berries of Sambucus nigra
and Ingustrum vulgare, which give a blue colour with all the
above reagents. A more careful investigation was made of the
berries of Ligustrwm. For this purpose the dried berries were
pounded and extracted with absolute alcohol. The alcohol extract
contained, in addition to chlorophyll, a crimson colouring matter,
which may be termed (A). When the alcohol ceased to be
coloured, the residue was dried again and then treated with water.
The filtrate was deep purple red and contained the greater part
of the colouring matter of the berries. The purple-red pigment
may be termed (B). The reactions of the two portions were
respectively as follows:
Basic lead acetate Alkalis Tron salts
(A) Green precipitate Green colouration Dull green colouration
(B) Blue Bf Blue a Blue 4
This result is comparable to those obtained by the following
authors :—
GRAFE" isolated a colouring matter—Malvenfarbstoff—from
the flowers of Althaea rosea by precipitation of the extract with
lead acetate and subsequent decomposition with sulphuretted
hydrogen. The pigment was separated into two portions differing
in their solubilities, 2.e.:—
Colouring matter (A) Colouring matter (B)
Soluble in alcohol Insoluble in alcohol but soluble in water
Cy4H i606 CoH 39013
The author regards (B) as a di-basic acid; the relationship
between the two pigments is shown in the following equations :—
(Ome. a H,O = C.H.O; SF CubhsOs;
———__
glucoside
QC HO! 2k 0)-4O.= Cre, On
156 Miss Wheldale, On the nature of anthocyanin.
From this we see that the pigment insoluble in alcohol is an oxi-
dation product and a glucoside of the pigment soluble in alcohol.
HEISE® obtained a pigment—Heidelbeerfarbstoff—from the
- Bilberry which was differentiated into two portions :—
Colouring matter (A) Colouring matter (B)
Insoluble in cold water, soluble in aleohol Soluble in water and alcohol
C1440; Co Hy40y2
The relationship is shown as :—
Cop H2,042 aie H,0 — CHO; 5 Cul OF
Oe
glucoside
GAUTIER" also extracted two pigments from the red leaves
of the Vine—Verfarbungroth der Rebblatter—and termed them
respectively :—
a-ampelochroie acid B-ampelochroic acid
Insoluble in cold water,
soluble in hot water Soluble in cold water
Green precipitate with Green precipitate with
basic lead acetate basic lead acetate
Dark green with iron salts Dark violet with iron salts
Ci9H 6010 C2gH23045
The results obtained from Ligustrum, Althaea and Vitis seem
to point to purple anthocyanin as being sometimes a mixture
of a red and bluer portion, the former giving a green-, the latter
a blue-iron reaction. The bluer portion is more soluble in water
and is generally present in greater quantity; this may explain
the iron-blueing reaction of some purple forms of anthocyanin.
The analyses made by GRAFE and by GAUTIER suggest that
the bluer pigment is more highly oxidised, and the change from
red to blue anthocyanin may possibly be one of oxidation
resembling the change which causes the colourless chromogen
to become red.
The separation of purple pigments into red and bluer con-
stituents is most obvious in the anthocyanin of certain allied orders,
z.e. Amarantaceae, Nyctaginaceae, Phytolaccaceae, and Portulacaceae.
The pigment of these genera differs in its reactions from the usual
type of anthocyanin* and is at the same time more readily
separable into two portions distinguished by means of their
respective solubilities in alcohol.
Pigment soluble in both
alcohol and water Basic lead acetate Aikalis Iron salts
AMATANTNUS SP... cc. cccevceees yellow precipitate ............... yellow...... green
Mirabilis Jalapa ............ orange-yellow precipitate...... vf seats s
Bougainvillea glabra ... orange seh \ 8 tiecenee ereene +
Phytolacca decandra ...... orange-red Pee PaO GAC yellow...... =
Portulaca grandijiora ,,.... orange Site | ace an) 5. -ebacc “
* Wheldale 2.
Miss Wheldale, On the nature of anthocyanin. 157
Pigment soluble in Basic lead Tron
water only acetate Alkalis salts
Amaranthus sp..........++ orange-red... yellow (purple with ammonia)... reddish
Mirabilis Jalapa ......... 5 was 93 a 33 is a
Bougainvillea glabra ... ved ............ purplish-green ...... cece cece ee ees Ae
Phytolacca decandra ... orange-red... yellow .........cscseeeeceseeeseecesees 563
Portulaca grandiflora ... 90 ee Bp} inbodddnboaco cdo oonsadscaseuDI0Ndo 20
There is evidently a tendency for the iron-greening reaction
to disappear as the pigment becomes more oxidised.
Collectively the results so far obtained as to the nature of
‘anthocyanin’ may be brought to bear upon the phenomena
observed in the genetics of flower-colour. In Lathyrus and
Matthiola (BATESON, SAUNDERS and PUNNETT*) red colour is
produced by the meeting of two factors C and R, of which C
has been regarded by the authors as possibly representing a
chromogen, and & the presence of an enzyme acting upon this
chromogen with the production of red pigment. If either the
chromogen or the enzyme be absent, then the plant has lost
the power of producing red pigment and constitutes an albino.
Moreover an additional factor B can be carried by the albino and
B co-existing with C and # can produce a blueing of the red
pigment. It seems possible that B may again be an enzyme
acting upon the red pigment to produce a bluer oxidation product
as we have seen in Althaea; in which, according to GRAFE, there
are two pigments, one the oxidation product of the other.
In Antirrhinum the albino (as regards anthocyanin) carrying
C, the chromogen, is distinguishable to the eye as the ivory-white.
In the true albino no chromogen is present and no aromatic
compound can be detected, but since the mating of an ivory-white
with an albino carrying & produces a magenta cross-bred, the
true albino probably carries the oxidising enzyme.
In the yellow variety of Antirrhinwm a similar yellow aromatic
substance 1s present as a derivative of that in the ivory; the
oxidation process in this case gives crimson as a result either
of the production of a different pigment or of red colouration
in the presence of unaltered yellow chromogen.
In Lathyrus and Matthiola, among the offspring produced
by the selfing of an individual heterozygous in C, # and in
the white plastid factor which is epistatic to cream, we find the
proportion of anthocyanic, z.e. purple and red, to non-anthocyanic,
i.e. white and cream, is as 9:7. Moreover among the non-
anthocyanic, the proportion of whites and creams carrying C
to those carrying A is as 1: 1.
Similarly in Antirrhinum, among the offspring from the
selfing of an individual heterozygous in the yellow chromogen
* Reports to the Evolution Committee of the Royal Society, 1—1Vv.
158 Miss Wheldale, On the nature of anthocyanin.
factor, in the factor modifying this to ivory and in AR, the
reddening factor, we find the proportion of anthocyanic, 2.e.
magenta and crimson individuals, to the non-anthocyanie, 2.¢.
ivory, yellow and white, is again as 9: 7.
Of the non-anthocyanic, the proportion of those carrying C,
ze. ivories and yellows, to those carrying R, we. true albinos,
is again as 1: 1.
Through the kindness of Professor Bateson and Mr R. P. Gregory,
who have been working for some time upon the inheritance of
flower-colour in Primula sinensis, I have lately been able to
examine a number of varieties of this genus. The flowers of
white varieties contain, as stated on p. 151, a chromogen apparently
of the nature of a flavone. Capability to produce red pigment—
anthocyanin—is probably due to the presence of an oxydase in the
plant; hence a white variety has either lost the power to produce
the oxydase or contains a positive factor—an inhibitor or re-
ductase—which prevents the formation of the pigment.
It is possible, on the one hand, that the loss of the oxydase
gives rise to certain white-flowered varieties with green stems.
These varieties are known as ‘recessive whites’; mated with a
full-coloured variety, such as deep crimson or magenta, they give
a full-coloured £,. On the other hand, the presence of an in-
hibitor in the flower only (as suggested by Bateson and Gregory),
may be the explanation of the existence of certain white-flowered
varieties having red stems; these varieties are termed ‘dominant
whites’ and mated with a full-coloured variety give an F, which is
only tinted.
When anthocyanin is present, two series of varieties are
distinguishable, a magenta series and a crimson series, the former
being epistatic to the latter. As previously stated, the same two
series, magenta and crimson, occur in Antirrhinwm and are probably
due to the action of an oxydase on the pale yellow flavone of the
ivory and the deep yellow flavone (xanthein) of the yellow varieties
respectively. In Primula no yellow (xantheic) variety arises from
the crimson but loss of oxydase from crimson and from magenta
gives whites indistinguishable to the eye, though those thrown
by magenta contain of course, the magenta factor,
I have examined the magenta and crimson pigments and also
the whites derived from each series. Whites from magenta appear
to carry a chromogen giving a more intense yellow with alkalis
than those from crimson; hence magentas give, on the whole,
a green colour with alkali, due to the blueing of the anthocyanin
and the yellowmg of the unaltered chromogen. The crimsons
give a bluer colour with alkali due to the far slighter yellowing
of the unaltered chromogen. The action of iron salts on the
crimson pigment results i a brown, on the magenta in a green
st
se | Pe
Miss Wheldale, On the nature of anthocyanin. 159
colouration. It is probable that magenta and crimson are different
pigments arising from the action of the same oxydase upon
different chromogens.
Hence we see that in Antirrhinum three non-anthocyanic
varieties exist. Ivory is a ‘white’ carrying the chromogen giving
rise to magenta; yellow is a ‘white’ carrying the chromogen giving
rise to crimson in oxidation and the true albino contains no
chromogen but probably only the oxydase.
There is some resemblance between Antirrhinum and Primula
in that one can detect in the latter two kinds of whites carrying
chromogens giving rise to magenta and crimson respectively but
the albino containing no chromogen has so far not been identified
in Primula and may not exist.
There is moreover a further resemblance as regards the blueing
factor; in both Antirrhinwm and Primula the crimsons and
magentas are of the purplish-red form of anthocyanin. When the
blueing factor is absent, varieties arise containing red anthocyanin *.
In Antirrhinum these are the ‘rose dorée’ (from magenta) and
‘bronze’ (from crimson). Similarly in Primula, loss of the blueing
factor gives rise to ‘pink’ (from magenta) and ‘orange king’ (from
crimson).
It is conceivable that the green-stemmed variety of Primula
may represent, in particular so to speak, a class of plants in general
which do not contain the requisite oxydase and hence can never
produce red pigment. Galanthus nwwalis, Narcissus poeticus,
Cucurbita Pepo, Helianthus annuus and numerous others would
be included in this class.
The red-stemmed white, on the contrary, may be the repre-
sentative of a class of plants which are anthocyanic but in the
flowers of which an inhibitor is present. Such plants have white
or nearly white flowers, though the stems and foliage may contain
more or less anthocyanin. Some marked examples of this class
would be Ozxalis acetosella, Geranium Robertianum var. album,
white cultivated Cyclamen persicum, Crataegus oxyacantha, Rosa
arvensis, Nymphaea alba, Angelica Sylvestris, and many other
Umbelliferae.
Loss of the inhibiting factor from this latter class would give
rise to a fully coloured variety from the white-flowered type, the
exact converse of the origin of a true albino from a coloured type.
Such cases are rather rare. The most striking examples are the
origin under cultivation of the deep red and magenta and of the
pink varieties from the original white-flowered Cyclamen persicum
which has red stems and leaves. The origin of the tinted Primula
acaulis from the wild type which has anthocyanin in its petioles
and leaf-stalks only.
* Wheldale
160 Miss Wheldale, On the nature of anthocyanin.
If the cultivated red varieties of Helianthemum vulgare are
derived from the yellow type, this would constitute a further
example. DE VRIES* quotes additional cases, 2.e. red varieties of
Achillea Millefolium, Begonia semperflorens, Crataegus oxyacantha,
Robinia Pseudacacia, and the red-leaved Beech and Hazel.
In conclusion I should like to take this opportunity of
expressing my thanks to Professor Bateson for his valuable advice
and help im this research. I am also indebted to Mr H. O. Jones
for suggestions in connection with the chemical portion of the
subject.
SUMMARY.
1. Chromogens, pale or deep yellow in colour (in the latter
case the so-called soluble yellow or xantheic pigments), and of
the nature of the flavone and xanthone classes of natural colouring
matters, are widely distributed in plants and are commonly found
in connection with the pink, purplish-red and purple series of
‘anthocyanic’ pigments.
2. These chromogens exist in the plant probably in com-
bination with various sugars, ze, as glucosides. Most of them
may be regarded as compounds of phloroglucin with protocate-
chuic acid, hydroxybenzoic acid or sometimes resorcylic acid.
Occasionally pyrocatechol or some other phenol takes the place
of phloroglucin.
DD)
3. OVERTON’S work on ‘anthocyanin’ from the point of view
of nutrition, also points to the conclusion that this pigment is
a glucoside compound of a tannic acid.
4. On the evidence of the recent work of PALLADIN in
connection with plant respiration, chromogens of an aromatic
nature are widely distributed and are able to produce red and
purple pigments when acted upon by the peroxydase of CHODAT
and BacH in the presence of available oxygen. Hence it is
highly probable that the bodies mentioned above may constitute
these chromogens.
5. Evidence from cross-breeding in Antirrhinum goes to
prove that for the production of the ‘anthocyanin’ of the type,
two bodies are essential, 7.¢., an aromatic chromogen of the
flavone series and a reddening factor, in all probability an
oxidising ferment.
* Species and Varieties, their Origin by Mutation.
Miss Wheldale, On the nature of anthocyanin. 161
6. Hence we may state that successive oxidation stages of
an aromatic chromogen probably give rise to the colour series,
pink, purplish-red, and purple of the more commonly occurring
form of ‘anthocyanin.’
7. An albino results either from the loss of the fundamental
chromogen or from the loss of the reddening enzyme from the
plant. The blueing enzymes depend for their manifestation on
the presence of both the first two factors.
8. In Antirrhinum and Phlox the albino carrying C, the
chromogen, is ivory-white in colour and is distinguishable from
the dead-white albino carrying R, the enzyme, not only chemically
but also in appearance. In Lathyrus and Matthiola no difference
in appearance can be detected between the albino carrying C and
the albino carrying #; in the two latter genera a thorough chemical
examination of the albinos has yet to be made.
9. The less commonly occurring scarlet ‘anthocyanin’ usually
gives no iron reaction; hence the difference in colour is probably
connected with a difference in constitution.
10. The later oxidation stages producing purple ‘anthocyanin’
are frequently accompanied by a change from an iron-greening to
an iron-blueing reaction. It is doubtful whether this is due to
total oxidation and disappearance of the iron-greening chromogen
or to a specific reaction of the ‘anthocyanin’ itself with iron salts.
BIBLIOGRAPHY.
1. Curren, G. “Recherches physiologiques sur la fleur.” Ann. des
Scr. naturelles, Série viu1., T. vi.
2. DeEnNeERT, HE. ‘Anatomie und Chemie des Blumenblatts.” Bot.
Centralb., 1889.
3. GautTizR, A. “Sur la coloration rouge éventuelle de certaines
feuilles et sur la couleur des feuilles d’automne.” Compt. Rend.
Acad. des Sciences. Paris. T. cxutt., 1906.
4. Icnimura, T. “On the Formation of Anthocyanin in the Petaloid
Calyx of the Red Japanese Hortense.” Jowr. Coll. of Sc. Imp.
Univ. Tokyo, Vol. xvut., 1903.
5. Miranpe, M. “Sur un cas de formation d’anthocyanine sous
linfluence d’une morsure d’insecte.” Compt. Rend. Acad. des
Sciences. Paris. T. cxutt., 1906.
“Sur Vorigine de Vanthocyanine déduite de lobservation de
quelques insectes parasites des feuilles.” Compt. Rend. Acad.
des Sciences. Paris. T. cxuv., 1907.
16
os)
10.
ge
»
Miss Wheldale, On the nature of anthocyanin.
Newsiery, M. I. “An Attempt to classify common Plant Pig-
ments with some Observations on the Meaning of Colour in
Plants.” Zrans. and Proc. Bot. Soc. Edinburgh, 1896.
Wiesner, J. ‘“Hinige Beobachtungen iiber Gerb- und Farb-stoffe
der Blumenblatter.” Bot. Zeit., 1862. 20.
Wiacanp, A. ‘Einige Sitze tiber die physiologische Bedeutung
des Gerbstoffes und der Pflanzenfarbe.” Bot. Zett., 1862.
“Die rothe und blaue Farbung von Laub und Frucht.” Boé.
Hefte. Forschungen a. d. bot. Garten zu Marburg, 1887.
Zorr, W. ‘Uber die Gerbstoff- und Anthokyan-behialter der
Fumariaceen und einiger anderen Pflanzen.” Bzrbliotheca Bo-
tanica, 1886. H. 11.
Overton, E. ‘“Beobachtungen und Versuche iiber das Auftreten
von rothem Zellsaft bei Pflanzen.” Prings. Jahr. f. wiss. Bot.,
1899.
Gautier, A. “Sur l’origine des matiéres colorantes de la vigne ;
sur les acides ampélochroiques et la coloration automnale des
végétaux.” Compt. Rend. Acad. des Sciences. Paris. T. cxiv.,
1892.
PrerFER. ‘ Physiology of Plants.”
Heisz, R. “Zur Kenntniss des Heidelbeerfarbstoffes.” Arbeit
a. d. Kaiserl. Gesundhettsamte, 1894.
Waacr, T. “Uber das Vorkommen und die Rolle des Phloro-
glucins in der Pflanze.” Ber. d. D. bot. Gesell., 1890.
Nicket, E. “Zur Physiologie des Gerbstoffes und der Trioxy-
benzole.” Bot. Centralb., 1891.
Brissemoret, A, “Sur une réaction colorée des tannoides.”
Bull. Soc. Chim. France, 1907.
Garpiner, W. ‘On the general Occurrence of Tannins in the
vegetable Cell.’ Proc. Cam. Phil. Soc., 1883.
GraFre, V. ‘Studien tiber das Anthokyan.” I. Mitt. Sttzwngs-
bericht d. k. Akad. d. wiss. Wien. Mat. nat. Kl. Bad. cxv.
Abt. 1., 1906.
Wue pate, M. ‘On the Inheritance of Flower-Colour in 4 éer-
rhinum majus.” Proce. Roy. Soc., Vol. uxx1x., 1907.
WHELDALE, M. “The Colours and Pigments of Flowers with
special reference to Genetics.” Proc. Roy. Soc., 1909.
Perkin, A. G. and Corr, F. “The Constituents of Artocarpus
integrifolia.” Part I. Jour. Chem. Soc. Trans., Vol. LXVIL,
1895.
Perkin, A. G. and Genparp, J. ‘‘A Constituent of Persian
Berries.” Jour. Chem. Soc. Trans., Vol. uxvu., 1895.
Perkin, A. G. and Patz, L. “Acid Compounds of some natural
yellow Colouring Matters.” Part I. Jour. Chem. Soc. T’rans.,
Vol. nxvir.,. 1895.
24,
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
Miss Wheldale, On the nature of anthocyanin. 163
Perkin, A. G. “Luteolin.” Part I. Jour. Chem. Soc., Vol.
Lx1x., 1896.
“Tuteolin.” Part II. Jour. Chem. Soc., Vol. uxix., 1896.
“Acid Compounds of natural Colouring Matters.” Part II.
Jour. Chem. Soc., Vol. tx1x., 1896.
Perkin, A. G. and Bagsiicu, H. “Morin.” Part I. Jour.
Chem. Soc. Trans., Vol. Lx1x., 1896.
Pernin, A. G. and Gunnextt, O. “The Colouring Matter of
Querbracho Colorado.” Jour. Chem. Soc. Trans., Vol. LX1x.,
1896.
Perxin, A. G. and Hummet, J. J. ‘The Colouring Principle
contained in the bark of Myrica nag.” Jour. Chem. Soc.
Trans., Vol, Lxix., 1896.
‘Occurrence of Quercetin in the outer Skins of the Bulb of
the Onion.” Jour. Chem. Soc. Trans., Vol. uxtx., 1896.
“The Colouring Matters occurring in British Plants.” Part I.
Jour. Chem. Soc. Trans., Vol. ux1x., 1896.
Prrxin, A. G. and Youne, G. ‘Colouring Matter of Sicilian
Sumach, Rhus Coriaria.” Jowr. Chem. Soc. T'rans., Vol. LxXix.,
1896.
Perkin, A. G. ‘Apiin and Apigenin.” Jour. Chem. Soc. Trans.,
Vol. txx1., 1897.
“The yellow Colouring Principles of various Tannin Matters.”
Jour. Chem. Soc. Trans., Vol. txxt., 1897.
“Yellow Colouring Matters obtained from Rhus rhodanthema,
Berberis Gtnensis and Rumex obtusifolius.” Jour. Chem. Soc.
Trons., Vol. uxxt., 1897.
Perkin, A. G. and Martin, H. W. ‘“ Rhamnazin.” Jowr. Chem.
Soc. Trans., Vol. uxxt., 1897.
Persin, A. G. ‘“Azobenzene Derivatives of some natural Colour-
ing Matters, Apigenin, Chrysin, Morin, Euxanthone and Gen-
tisin.” Jour. Chem. Soc. Trans., Vol. uxxt.,. 1898. “The
yellow Colouring Matters contained in various Tannin Matters.
Rhus cotmus and &. rhodanthema.” Jowr. Chem. Soc. Trans.,
Vol. uxxu1., 1898.
Perrin, A. G. and Pinerim, J. A. “The Colouring Matters of
the Indian Dye-stuff Asbarg, Delphinwwm Zalil.” Jour. Chem.
Soc. Trans., Vol. uxx111., 1898.
Perkin, A. G. and Woop, P. J. ‘Yellow Colouring Principles
contained in various Tannin Matters. Pistacia lentiscus,
P. terebinthus, Tamaris africana, T. gallica, Ailanthus glan-
dulosa, Ficus carica.” Jour. Chem. Soc. Trans, Vol. uxxttt.,
1898.
Perkin, A. G. and Newsury, F. G. ‘Colouring Matters con-
tained in Dyer’s Broom, Glenista tinctoria and Heather, Calluna
vulgaris.” Jour. Chem. Soc. Trans., Vol. uxxv., 1899.
164
35.
36.
37.
38.
39.
40.
41.
42.
43.
44,
45,
Miss Wheldale, On the nature of anthocyanin.
Pergin, A. G. “Apiin and Apigenin,” Part II. Jour. Chem.
Soc. Trans., Vol. uxxvit., 1900.
“Yellow Colouring Principles contained in various Tannin
Matters. Arctostaphylos Uva ursi, Haematoxylon Campeachi-
anum, Khus Metopium, Myrica gale, Coriaria myrtifolia, and
Robinia pseudacacia.” Jowr. Chem. Soc. Trans., Vol. uXxvit.,
1900.
Perkin, A. G. and Horseratt, L. H. “Genistein.” Part IL
Jour. Chem. Soc. Trans., Vol. uxxvit., 1900. ‘Luteolin.”
Part ITI. Jour. Chem. Soc. Trans., Vol. uxxvu., 1900.
Perkin, A. G. and Witkinson, E. J. “The Colouring Matter of
the Flowers of Delphinium Consolida.” Jour. Chem. Soc. Trans.,
Vol. uxxxt., 1902.
Perkin, A.G. “Myricetin.” Part II. Jour. Chem. Soc. Trans.,
Vol. uxxx1., 1902. ‘“Robinin, Viola Quercitrin, Myrticolorin
and Osyritrin.” Jour. Chem. Soc. Trans., Vol. LXxx1., 1902.
“Notes on Luteolin and Apigenin.” Jour. Chem. Soc. Trans.,
Vol. uxxxt., 1902.
Perkin, A. G. and Atuison, J. R. “Rhamnazin and Rhamnetin.’
Jour. Chem. Soc. Trans., Vol. txxxt., 1902.
Perkin, A. G. and Purpps, 8. ‘Some Natural Colouring Matters.”
Jour. Chem. Soc. Trans., Vol. uxxxv., 1904. .
?
Brpeoop, J. ‘Floral Colours and Pigments.” Jour, Roy. Hort.
Soc., Dec. 1905.
Naytor and Cuappet. “Note on the Colouring Matter of Rosa -
gallica.” Pharm. Jour. 1904.
PaLLapin, W. “Die Verbreitung der Atmungschromogene bei
den Pflanzen.” Ber. d. D. Bot. Gesell., July 1908.
“Uber die Bildung der Atmungschromogene in den Pflanzen.”
Ber. d. D. Bot. Gesell., July 1908.
Brerrranp, G. ‘Sur les rapports qui existent entre la con-
stitution chimique des composés organiques et leur oxydabilité
sous l’influence de la laccase.” Comp. Rend. Acad. des Sciences.
Paris, 1896.
“Recherches sur la laccase, nouveau ferment soluble 4 pro-
priétés oxydantes.” Annales de Chimie et de Physique. 7 Série.
1897.
Cuopat, R. “Les ferments oxydants.” Jour. Suisse de Chimie
et Pharmacie, 1905.
“ Nouvelles recherches sur les ferments oxydants.” Arch. des
sciences physiques et naturelles, 1907.
“Zur specifischen Wirkung der Peroxydasen—eine Prioritits-
frage.” Ber. d. D. Chem. Gresell., July, 1906.
Miss Wheldale, On the nature of anthocyanin. 165
46. CuHopat, R. und Bacu, A. “Untersuchungen tiber die Rolle der
Peroxyde in der Chemie der lebenden Zelle.” Ber. d. D. Chem.
Gesell., 1903, 1904.
“Recherches sur le rdle des peroxydes dans l’économie de la
cellule vivante.” Arch. des sciences physiques et naturelles, 1902.
47. De Srorckuin, E. ‘Contribution 4 l'étude de la peroxydase.”
Université de Geneve—Institut de Botanique, 1907.
ADDITIONAL BIBLIOGRAPHY, IN CONNECTION
WITH PLANT PIGMENTS.
ApriAN et Trittat. ‘Sur la matiére colorante de la Digitale.” Compt.
rend. Acad. des Sciences. Paris. T. cxxix., 1899.
Asxenasy, E. “Uber den Einfluss des Lichtes auf die Farbe der
Bliithen.” Bot. Zeit. 1876.
Bavsr, K. ‘Untersuchungen iiber Gerbstofffiihrende Pflanzen.’
Osterreichische Bot. Zeitschrift. xu. Wien, 1890.
Boum. ‘‘Physiologische Untersuchungen tiber blaue Passiflorabeeren.”
Sitzungsber. der Kaiserl. Akad. der Wissenschaft. Wien, 1857.
CiaupEL, L. ‘Sur les matieres colorantes du spermoderme dans les
Angiospermes.” Compt. rend. Acad. des Sciences. Paris. T. c1x.,
1889.
Finnon, E. “Observations sur les matiéres colorantes des fleurs.”
Compt. rend. Acad. des Sciences. Paris. T. xxx1x., 1854.
“‘ Note sur quelques matiéres colorantes végétales.” Compt. rend.
Acad. des Sciences. Paris. T.1., 1860.
“Nouvelles recherches sur les matiéres colorantes végétales.”
Compt. rend. Acad. des Sciences. Paris. T. u., 1860.
Frimy, E. und Croiz. “Uber die Farbstoffe der Blumen.” Jour. fiir
praktische Chemie, 1854.
Fritscu, P. “Uber farbige kirnige Stoffe des Zellinhalts.” Prings.
Jahr., 1883. :
Gautier, A. “Sur les matiéres colorantes des vins.” Compt. rend.
Acad. des Sciences. Paris. 'T. uxxxvi., 1878.
Gertz, O. “ Ett nytt fall af Kristalliseradt Anthocyan.” Botaniska
Notiser. H. vi., 1906.
“Studier 6fver Anthocyan.” Akademisk Afhandling. Lund, 1906.
?
Gittot, X. “Observations sur la coloration rosée ou érythrisme des
fleurs normaliment blanches.” Bull. de la Soc. bot. de France.
Xt. LOos.
Grirritus, A. B. “Die Pigmente des Geraniums und anderer Pflanzen.”
Ber. d. D. Chem. Gres., xxxvi., 1908.
166 Miss Wheldale, On the nature of anthocyanin.
Grirron, E. “L/assimilation chlorophyllienne et la coloration des _
plantes.” Ann. des Sciences naturelles. Bot. Sér. vuit., T. x., 1899.
eee A. ‘Die Farbstoffe der Bliithen und Friichte.” Wiirzburg,
1884.
Hinpeprann, F. “Anatomische Untersuchungen iiber die Farben der
Bliithen.” Prings. Jahr., 1863.
“Die Farben der Blitthen.” Leipzig, 1879.
“Uber einige merkwiirdige Farbungen von Pflanzentheilen.”
Ber. d. D. Boe: Gesell., 1883.
Hincrr, A. ‘Zur Ligaen Kenntniss der Blumenfarbstoffe.” Bot.
Centralb., 1894.
Karzet, R. ‘“Beitrige zur Kenntniss des Anthokyans in Bliithen.”
Osterreich. bot. Zeitschrift, 1906.
Keresie, F. W. “The Red Pigment of Flowering Plants.” Sct. Prog.
Vol. 1. New Series.
Kyy, L. “Uber Laubfarbungen.” Naturwissenschaftlichen Wochen-
schrift. Vierter Band, 1889. Berlin.
“Zur physiologischen Bedeutung des Anthocyans.” stratto
daglt Atti del Congresso Botanico Internazionale. 1892.
Kout, G. ‘Untersuchungen iiber das Carotin und seine physiologische
Bedeutung in der Pflanze.” 1904.
Kraemer, H. “The Origin and Nature of Color in Plants.” Proc.
Amer. Phil. Soc., LX11., 1904.
Kraus, C. ‘‘Uber die Ursache der Farbung der Epidermis vegetativer
Organe der Pflanzen.” Flora. 1873.
Kraus, G. ‘‘Die Entstehung der Farbstoffkérper in den Beeren von
Solanum pseudocapsicum.” Prings. Jahr., viii.
Kroremer, K. ‘Uber das angebliche Vorkommen von THE OLE Chro-
matophoren.” Bot. Centralb., 1900.
Kurscurr, E. “Uber die Verwendung der Gerbsiure im Stoffwechsel
der Pflanze.” Flora, 1883.
Lepet, F. von. ‘ Pflanzenfarbstoffe als Reagentien auf Magnesium
Salze.” Ber. d. D. Chem. Gesell., 1880.
Linspauver, lL. ‘“Hinige Bemerkungen wtber Anthokyanbildung.”
Osterreich. Bot. Zeitschrift, 1901.
MarsHALL-Warp and Dats, E. “On Craterostigma pumilum.” Trans.
Linn. Soc., Vol. v.
Mer, E. ‘Recherches sur les causes des colorations diverses qui
apparaissent dans les feuilles en automne et en hiver.” Bull. de
la Soc. bot. de France, 1877.
Meike, G. “Uber die Stellung der Gerbsiuren im Stoffwechsel der
Pflanzen.” Bot. Cenétralb., 1894.
Mivosn1, M. “Uber die kiinstliche Aenderung der Bliithenfarben.”
Bot. Centralb., Bd. txxxt111., 1900.
Miss Wheldale, On the nature of anthocyann. 167
Mostus, M. “Uber den Glanz der gelben Ranunculus-bliithen.” Bot.
Centralb., 1885.
“ Die Farben in der Pflanzenwelt.” Berlin, 1900.
“ Das Anthophaein, der braune Bliithenfarbstoff.” Ber. d. D. Bot.
Gesell., 1900.
Mout, H. V. “Uber die blaue Farbung der Friichte von Viburnum
Tinus.” Bot. Zeit., 1870.
Mouscu, H. ‘Uber den Farbenwechsel anthokyanhaltiger Blatter
bei rasch eintretendem Tode.” Boé. Zeit., 1889.
“Blattgriin und Blumenblau.’’ Vortrdge des Vereines zur Ver-
breitung naturwissensch. Kenntnisse in Wien, xxx. Jahrg. 1890,
ES
“Die Krystallisation und der Nachweis des Xanthophylls (Caro-
tins) im Blatte.” Ber. d. D. Bot. Gesell., Bd. x1v., 1896.
“Der Einfluss des Bodens auf die Bliithenfarbe der Hortensien.”
Bot. Zeit., 1897.
“Uber ein neues, einen carminrothen Farbstoff erzeugendes Chro-
mogen bei Schenckia blumenaviana.” Ber. d. D. Bot. Gesell., 1901.
“Uber amorphes und kristallisiertes Anthokyan.” Bot. Zeit., 1905.
Montanari, ©. ‘Materia colorante rossa del pomodoro.” Staz.
sperim. agrarie. Modena, Vol. xxvu., 1904.
Morot, F. S. “Recherches sur la coloration des végétaux.” Ann.
des Sciences naturelles. Série 11., T. x11., 1849.
Miier, N. J. C. “Spectralanalyse der Bliithenfarben.” Prings.
Jahr., 1889.
Newsiein, M.I. ‘Colour in Nature.” 1898.
PanTANELLI, E. “Studii sul’ albinismo nel Regno Vegetale.” Mal-
pighia. Vols. XV., XVI., XVII., XVIII. and XIX.
Pick, H. “Uber die Bedeutung des rothen Farbstoffes bei den
Phanerogamen und die Beziehungen desselben zur Stérkewan-
derung.” -Bot. Centralb., 1883.
Pim, G. “Cell-sap Crystals.” Journ. of Bot., Vol. xxt1., 1884.
Portneim, L. von und Scuoit, E. “Untersuchungen tiber die Bildung
und den Chemismus von Anthokyanen.” er. d. D. Bot. Gesell.,
July, 1908.
Rernitzer, F. “ Bemerkungen zur Physiologie des Gerbstoffes.” Ber.
d. D. Bot. Gesell., 1889.
Rosanorr, 8. ‘Zur Morphologie der Pflanzenfarbstoffe.” Bot. Zeit.,
1870.
Scuimeer, A. F. W. “Uber die Entwickelung der Chlorophyllkorner
und Farbkorper.” Bot. Zeit., 1883.
“Untersuchungen tiber die Chlorophyllkorper und die ihnen
homologen Gebilde.” Prings. Jahr., 1885,
VOL. XV. PT. II. 12
168 Miss Wheldale, On the nature of anthocyanin.
Scunerzier, J.B. “Uber den rothen Farbstoff der Blatter von Ampe-
lopsis hederacea.” Bot. Centralb., 1880.
“Uber Veranderungen des rothen Farbstoffes von Paeonia officinalis
unter dem Einfluss chemischer Reagentien.” ot. Centralb., 1880.
ScHrOTTER-KRISTELLI, H. R. “Uber ein neues Vorkommen von Carotin
in der Pflanze.” Bot. Centralb., 1895.
Sorsy, H. C. “On a definite Method of qualitative Analysis of
animal and vegetable Colouring-matters by means of the Spectrum
Microscope.” Proc. Roy. Soc., 1867.
“On comparative vegetable Chromatology.” Proc. Roy. Soc.,
1873.
STaut, E. “Uber bunte Laubblitter.” Annales du Jardin Bot. de
Buitenzorg, Vol. xut., 1896.
Tames, T. ‘Uber die Verbreitung des Carotins im Pflanzenreiche.”
Flora, 1900.
TiscHLER, G. ‘Uber die Beziehungen der Anthocyanbildung zur
Winterharte der Pflanzen.” Bethefte zwm Bot. Centralb., Bd.
xvi., 1905.
Tont, J. B. pe. “Observations sur l’anthocyane d’Ajuga et de Strobi-
lanthes.” Compt. rend. Ass. frangaise Avanc. Sc., Paris, 1907.
TREVIRANUS, L. C. “Uber den Wechsel des Griinen und Rothen in den
Lebenssiften belebter Korper.” Bot. Zeit., 1860.
Weiceet, L. “Beitrage zur Chemie der rothen Pflanzenfarbstoffe.”
Jahresber. der K. K. énolog. und pomolog. Lehranstalt zu Kloster-
neuberg bei Wren, 1894—95.
Weiss, A. “Untersuchungen iiber die Entwickelungsgeschichte des
Farbstoffes in Pflanzenzellen.” Sitzwngsberichte der Kaaserlichen
Akademie der Wissenschaften. Math-natur. Classe. Bd. ttv. I.
Abtheilung, Wien, 1866.
Wiesner, J. ‘Untersuchungen iiber die Farbstoffe einiger fiir chloro-
phyllfrei gehaltenen Phanerogamen.” Prings. Jahr., 1872.
Mr Kleeman, The nature of the iomsation, etc. 169
The nature of the tonisation produced in a gas by y rays.
By R. D. Kuremay, B.A., D.Sc., Emmanuel College, Cambridge.
(Communicated by Professor Sir J. J. Thomson, F.R.8.)
Read 8 March 1909.
a
The ionisation in a chamber placed in the path of y rays may
consist of three parts. One part may consist of ions ejected by
the y rays from the gas molecules with a velocity which is so
small that they are unable to produce any further ions themselves.
One of the other parts must consist of ions made by the cathode
rays from the walls of the chamber, and the third part of ions
made by the cathode rays of high velocity ejected from the gas
molecules. The first of these parts is proportional to the mass
of the gas and therefore proportional to the pressure, and this is
also true for the second part since the ionisation of a gas by 8
rays has been shown to be proportional to the pressure. Since
the number of electrons ejected from the gas is proportional to
the pressure, and the number of ions each produces proportional
to the pressure, the third part is proportional to the square of the
pressure. The ionisation in the chamber may therefore be expressed
in the form {(A + B) p + Cp”}, where p denotes the pressure.
Laby and Kaye* have shown that the ionisation in air and
carbon dioxide is proportional to the pressure over a wide range
of pressures. The term Cp? is therefore small within this range.
Experiments on the variation of the ionisation with pressure will
not however give any information as to the relative values of
A and B, since both the ionisation produced by the secondary
cathode radiation from the walls of the chamber and that due
to the ejection of slow-moving ions from the molecules of the gas
by the y rays vary as the pressure. Attempts have been made
to obtain an estimate of the amount of ionisation in a chamber
which is not due to the radiation from the walls. All these
estimates depend on some calculations based on certain assump-
tions, generally involving the absorption, ionisation, etc., of the
cathode rays produced by the y rays. Now the writer has shown
in a paper in the course of publication} that the y rays give rise
to secondary cathode rays of very different velocities, some of
these rays have a range in air at atmospheric pressure of the
order of 2 cm. while some are as penetrating as the penetrating
B rays of radium. It cannot be assumed therefore that the
* Phil. Mag. p. 879, Dec. 1908.
+ Read before the Royal Society,
12—2
170 Mr Kleeman, The nature of the tonisation
absorption of the rays as a whole is the same as the @ rays of
uranium, or the penetrating 8 rays of radium. These calculations
are therefore not satisfactory, they may easily be very considerably
out. In fact McLennan* deduced that the ionisation in a chamber
not due to the secondary radiation from the walls is equal to
about one half of the total ionisation in the chamber, while Wilson}
makes it equal to one sixth of the total ionisation. It does not
therefore appear quite certain that the total ionisation is not due
entirely to the secondary radiation from the walls. The writer
therefore made some direct experiments to test this point.
Several slightly different arrangements were used, each of
which involved the deflection of the secondary radiation from
the apparatus by means of a magnetic field. A diagram of the
apparatus first used is shown in figure 1. A is an ionisation
< \
AE
HK
if
Fig. 1.
chamber on a lead block B, 5 cm. thick, the chamber being placed
symmetrically with respect to an aperture a in the block. 30
mgrm. of radium were placed at C underneath the aperture. A
magnet whose poles measured 5°5 cm. by 5°5 cm., was placed so
that the lines of magnetic force traversed the chamber. Since
the electrons produced by y rays are ejected in the direction of
* Phil. Mag. Dec. 1907.
+ Phil. Mag. p. 216, Jan. 1909.
produced in a gas by y rays. 171
propagation of the rays, there was a diffuse pencil of @ rays
projected into the chamber from its lower side. If the ionisation
is produced by the @ rays from the walls of the chamber, the
ionisation ought to be principally due to this beam, and should
therefore decrease considerably when a strong magnetic field is
applied. It was found, however, that a magnetic field produces
little change in the amount of ionisation. Thus in a particular
case the ionisation in a sheet lead chamber 5:5 cm. high, 5:5 cm.
broad, and 7°5 cm. long, was 1895 in arbitrary units. When a
field of over 2000 units was applied, which was sufficient to bend
the rays having the same velocity as the penetrating @ rays from
radium into a circle of radius less than 8 mm., the ionisation
current decreased to 1645, or about 12°/,. When a chamber
7 cm. high, 4 cm. long, and 3 cm. broad was used, the current
changed from 1560 to 1475, when the magnetic field was applied,
a decrease of about 6°/..
If all the ionisation in the gas was produced by the @ rays
from the walls of the chambers, the ionisation should obviously
have decreased to a greater extent in each case, although a part
of the path of each ray when deflected was still contained by
the chamber, and consequently produced ionisation.
Since part of the leak in this experiment was always due
to the @ rays from the walls of the ionisation chamber, it was
thought desirable to carry out the experiment in a somewhat
different form. Figure 2 gives a diagram of the apparatus used.
A is a cylindrical ionisation chamber 19 cm. long, and 8 em. in
diameter, to which the tube ab 6°5 cm. long and 3°5 cm. in diameter
was co-axially attached. The chamber was placed so that the
tube ab was between the poles of an electro-magnet. The end
a of the tube was closed in one set of experiments by a sheet
of thin aluminium leaf equivalent in mass to a layer of air ‘7 cm.
thick, the end b of the tube being closed with a metal plate c.
172 Mr Kleeman, The nature of the ionisation
The end d of the chamber A was closed with a thin sheet of zine.
B is a lead block 3 em. thick through which a circular hole e was
drilled about 1 cm. in diameter. The axis of this hole and the
glass tube C containing 30 mgrm. of radium (which was surrounded
by sheet lead 2 mm. thick), were placed co-axially with the tube
ab and the ionisation chamber A. The ionisation in the chamber
was produced principally in the cone / by the y rays from the
radium and the secondary @ rays from the plate c, the secondary
8 rays being initially projected in the direction of propagation
of the y rays*. The secondary @ rays produced in a plate are to
some extent scattered by the plate, but the larger part of the
radiation proceeds approximately in the direction of propagation
of the rays. Thus the writer has shown in the paper above
mentioned that the pencil of secondary 8 rays emerging from
a plate placed at one end of an aperture in a thick lead block
while the radium is placed at the other end, is almost exactly
of the same form as that obtained by shooting the @ rays from
the radium through the aperture. The larger part of the radiation
from the plate c therefore entered the chamber.
The measurements were carried out by first placing a lead
plug into the hole e of the lead block B and measuring the leak
in the chamber. This gives the leak in the chamber due to
imperfect screening of the lead block B. The leak was then
measured with the plug removed. The difference between this
leak and the former gave the ionisation in the cone f due directly
to the y rays and the secondary rays from the plate c. A magnetic
field of sufficient strength to bend the 8 rays from c so that they
did not enter the chamber A, was then applied, and the leak again
measured. The difference between this leak and the first gave
the leak in the cone approximately due to the direct action of the
y rays.
Whether the strength of the magnetic field was sufficient
to bend the 8 rays from the lead plate ¢ so that they did not
enter the chamber A was tested as follows. The plate c and the
lead sheeting surrounding the radium was removed so that a pencil
of 8 rays from the radium now penetrated into the chamber.
When the current used in these experiments was switched on
to the magnet the ionisation was decreased to about 20°/, of its
original amount, showing that practically all the @ rays were
prevented from entering the chamber by the magnetic field.
Firstly some measurements were made with no aluminium
leaf placed at a. It was found that using a lead plate at ¢
2mm. thick, the ionisation in the cone f decreased 15°/,, when
the current was switched on to the magnet; when the plate was
of aluminium 3 mm. thick, the decrease was 23 °/..
* Bragg and Madsen, Trans. Roy. Soc. of S. Australia, Vol. xxxu. Jan. 1908.
produced in a gas by y rays. 173
An aluminium leaf was then placed at a, the ionisation in the
tube ab being now excluded from the leak. The decrease obtained
with a lead radiator when the magnetic field was applied was
23 °/,, and 31°/, with the aluminium radiator.
The secondary 8 radiation from the thin zine wall d of the
ionisation chamber produced by the cone of y rays f was much
smaller than that from the plate c because the zine wall was much
thinner than the plate, and also because the returned @ radiation
from a plate is much smaller* than the radiation which is
propagated in the same direction as the y rays, the difference
being the greater the thinner the plate. The figures obtained
Fig. 3.
show therefore that more than 50°/, of the ionisation in the cone
f is due to the direct action of the y rays on the air.
Some further measurements were carried out with a slight
modification of the foregoing experiment. A diagram of the
modified apparatus is shown in figure 3. A is an ionisation
chamber 10°5 cm. long, 10°4 cm. broad, and 7 cm. deep, of which
the upper and lower sides consisted of thin tightly stretched
* Trans. Roy. Soc. of S. Australia, 1908, Pt. 1.
174 Mr Kleeman, The nature of the ionisation
tissue paper, equivalent in mass to a layer of air 1 cm. thick.
The chamber was placed on the poles B, and B, of an electro-
magnet, which were resting on a lead block C 5 cm. thick. This
lead block had an aperture a 3 cm. by 3:2 cm., which was placed
in a symmetrical position with respect to the poles of the electro-
magnet and the ionisation chamber. D is the tube containing
the radium placed at a distance of 10 cm. from the lead block.
The electrode of the chamber consisted of a wire bent into the
form of a square so that the principal stream of y rays through
the aperture did not impinge upon it. The ionisation in the
chamber was, as before, principally due to the direct ionisation
of the gas by the y rays and the secondary 8 rays from the plate
b placed over the aperture a. The plate 6 was of aluminium
4 mm. thick.
The readings were carried out in exactly the same way as
in the foregoing experiment. The ionisation in the cone c
decreased to about 55°/, of its original value, when a magnetic
field of sufficient strength to prevent the @ rays from the plate
b entering the chamber was applied. This remaining ionisation
is almost entirely due to the action of the y rays on the air in
the cone c, the ionisation by the secondary radiation from the
tissue paper being negligible since the paper is equivalent in mass
to less than a third of the air in the chamber while the ionisation
by the penetrating radiation from the air in a chamber of ordinary
size 1s negligible.
The returned cathode radiation from the air outside the
chamber may for our purpose be neglected in comparison with
the radiation from the aluminium plate b. For if we assume
that the air is equivalent to a carbon plate giving the maximum
amount of radiation placed on top of the chamber, the returned
radiation is about ; of the emerging radiation*. In the case
of air it will be less than that, since it radiates to a larger extent
sideways than the carbon plate. Now, at least one half of the
radiation emerging from the aluminium plate b enters the cham-
ber, and if we take the amount of emergence radiation of a plate
of carbon and aluminium the same, which is approximately true,
the returned radiation from the air is less than one-sixth of the
radiation from the aluminium plate.
It appears therefore from these experiments that the ionisation
in a chamber is due in part to the direct action of the y rays on
the gas it contains. And since Laby and Kaye have shown that
the amount of ionisation produced by the secondary y and 8
radiation from the gas is small, this ionisation consists of slow-
moving 8 rays ejected by the y rays, which have not sufficient
velocity to produce any further ionisation themselves.
* Bragg and Madsen, Trans. R. Soc. of South Australia, Vol. xxx1. p. 4, 1908.
produced in a gas by y rays. 175
The ratio of this part of the ionisation in a chamber to that
produced by the radiation from its walls, will depend on the ratio
of the total inside surface of the walls of the chamber to its
volume, and other conditions. The numbers obtained in the
experiments just described suggest, however, that in most cases
this ratio will probably be greater than one half, or the ionisation
produced directly by the primary y rays is in most cases greater
than 50°/, of the total ionisation.
The connection of this result with other quantities will now
be considered.
Eve* has made a determination of the total number of ions
produced per second by the y rays from a gram of radium bromide
in a volume of air which completely absorbs the rays. He
measured the ionisation in a cylindrical chamber 51 cm. high
and 23 cm. in diameter, the chamber being made of sheet
aluminium ‘4 mm. thick. Assuming the absorption of the vy rays
by air to be the same as an equal mass of aluminium—whose
coefficient of absorption is known—and knowing the volume of the
chamber and its distance from the radium, etc., the number of
ions produced per second by the y rays of a gram of radium could
be calculated. In this way Eve obtained 8°9 x 10“ for the number
of ions produced.
The results obtained in this paper suggest that the ionisation
in his chamber due to the 6 rays produced directly by the y rays,
was roughly about half of the total ionisation; or, the number of
6 rays produced per second directly by a gram of radium is equal
to 44 x 10“. This number should be as near (if not nearer) to the
true value of this quantity, as that given by Eve for the total
number of ions produced by the y rays of a gram of radium, in
which case the penetrating 8 rays from the gas are supposed
to spend all their energy in ionisation.
Crowthert has shown that the amount of ionisation produced
by the secondary radiation from the molecules of a gas exposed to
X rays is small in comparison with the total amount of ionisation
produced, and that the ionisation in a gas is therefore principally
due to the direct action of the X rays.
This can be shown to be true also in the case of @ rays.
The ionisation of the gas in a chamber exposed to 8 rays may
be divided into two parts. One part consists of slow-moving ions
or 6 rays produced directly by the primary 8 rays and the
secondary 8 rays from the walls of the chamber. The other part
consists of the ionisation produced by the B rays of high velocity
ejected from the molecules of the gas. The first part is propor-
tional to the pressure, while the second part, from what has gone
* Phil. Mag. p. 192, Sep. 1906.
+ Proc. Camb. Phil. Soc. p. 34, Vol. xv. Pt. 1, 1908.
176 Mr Kleeman, The nature of the tonisation
before, is proportional to the square of the pressure. Now, Strutt*
has shown that the ionisation in a gas by 8 rays is proportional
to the pressure over a wide range of pressures. The second part
of the ionisation is therefore small in comparison with the first.
Thus the 8 rays also produce directly rays which do not themselves
possess sufficient velocity to make any further ions.
Thus the ionisation of a gas by y, 8, or X rays, is a measure
of the number of 8 rays produced directly by the ionising agent.
Since these rays are not able to produce any further ions
themselves they must have a velocity less than 2°7 x 10° cm./sec.,
for at higher velocities, according to Townsend, ions are produced
by collision.
The writert has shown that the y rays of radium produce
cathode rays of very different velocities, the maximum velocity
being equal to that of the penetrating 8 rays from radium. It
appears therefore that the y rays produce cathode rays ranging in
velocity from 2°7 x 108 to 2:9 x 10" cm./sec.—the velocity of the
penetrating 8 rays from radium. In the case of X rays cathode
rays are produced probably ranging in velocity from 2-7 x 108 to
83 x 10° cm./sec., the latter velocity being that obtained by Innes
for the penetrating cathode rays from a plate exposed to X rays.
Since the most penetrating cathode rays ejected by X rays
have a range in air at atmospheric pressure equal to a fraction of
a mm. only, the rays produced in the gas contained in an ionisation
chamber are entirely absorbed by the gas. The ionisation in
a gas by X rays is therefore a measure of the energy converted
directly into cathode rays. Now, according to Crowther, the
ionisation produced by the secondary cathode rays which are able
to produce ions by collision is small in comparison with the
ionisation produced directly by the X rays. It follows therefore
that the energy expended in the production of penetrating cathode
rays is small in comparison with that expended in the production
of 6 rays. And since the energy of one of the most penetrating
cathode rays ejected by X rays is about 900 times that of a 6 ray,
the number of penetrating cathode rays ejected must be very
small indeed in comparison with the number of 8 rays ejected.
Whether this is also true for the cathode rays ejected by
y rays cannot yet be determined since there are not sufficient
experimental data. The penetrating cathode rays ejected by
y rays are not absorbed in a distance of a fraction of a mm. in
a gas like those ejected by X rays, but are able to cross an
ionisation chamber without any appreciable absorption. And
since the ionisation they produce in a chamber is small in
comparison with the total ionisation, this quantity is, provided
* Phil. Trans., A, vol. 196, p. 507, 1901.
+ loc. cit.
produced in a gas by y rays. 177
the effect of the secondary radiation from the walls of the
chamber is eliminated, a measure of the energy from the y ray
beam converted directly into 6 rays. The energy converted into
penetrating cathode rays may however be (in the case of y rays)
comparatively large, even if a comparatively small number of
§ rays are produced, for the energy of one of the most penetrating
rays is about 2000 times that of a 6 ray.
The coefficient of absorption of a plate of material placed in
the path of a beam of y rays is a measure of the energy converted
into energy of 6 rays, penetrating cathode rays, and other forms
of radiation. The ionisation values for different gases, since they
are only a measure of the energy converted into energy of 6 rays,
cannot therefore be compared with the coefficient of absorption
of materials without any knowledge of the comparative magnitude
of the energies of these radiations. Some information on the
subject could be obtained by comparing the coefficients of
absorption of liquids with the ionisations of their vapours.
It is not improbable that the ejection of penetrating cathode
rays by y rays and X rays is accompanied by the production of
secondary y and X rays, and it would be interesting therefore,
when sufficient data are available, to compare the relative
secondary y and X radiations from different materials with the
relative penetrating cathode radiations produced, in order to see
how much of the secondary y and X radiation is accounted for
in the above way.
178 Mr Doncaster, Note on an abnormal
Note on an abnormal pair of appendages in Inthobius. By
L. Doncaster, M.A., Lecturer on Zoology, Birmingham University.
[Received 15 March 1909.]
In dissecting a specimen of the common English Centipede
(Iathobius forficatus), a student in the Birmingham Zoological
Laboratory found that it had an extra pair of appendages between
the poison-claws and the second maxillae. I did not see the
specimen before the appendages were removed, so cannot say
exactly how they were attached. The additional pair is repre-
sented in fig. 1, from a camera-drawing, and fig. 2 represents the
Fig. 1. Fig. 2.
poison-claws of the same specimen on the same scale. It will be
seen that the extra appendages are more nearly like poison-claws
than any other appendages of Jnthobius, but differ in several
important details. They are much smaller, are differently jointed;
and instead of ending in one sharp tooth on which the poison-ducet
opens, they have at their extremity a triple tooth in which no
duct is visible. It should be said that they had been soaked in
potash before they were carefully examined so that a rudimentary
poison gland and duct might have been present and destroyed.
Another point of interest concerns the median part of the
pair of appendages in Inthobius. 179
appendage. The basal joints of the two sides are more completely
fused than are the poison-claws, and in the position where the
latter bear six small processes or teeth on each side, the extra
appendages bear on each side two larger teeth, which have the
appearance of being jointed on to the base of the appendage, and
are not mere processes of it as they are in the normal pair.
The mandibles and both pairs of maxillae appeared to be
perfectly normal, and behind the normal pair of poison-claws
there were as usual fifteen pairs of walking legs.
180 Mr Boulenger, On the migration of the thread-cells, etc.
On the migration of the thread-cells of Mcerisia. (Preliminary .
note.) By C. L. BoULENGER, B.A., King’s College.
[Read 22 February 1909.]
In a recent paper whilst describing the structure of the
Egyptian medusa Merisia lyonsi I called attention to the fact
that large nematocysts were constantly to be found among the
endoderm cells of the manubrium. Careful examination of a
larger series of sections has convinced me that these nematocysts
are in process of migration through the tissues, a phenomenon
similar to that recently described by Hadzi in hydroids.
The main thread-cell batteries in Merisia are those around
the oral opening and those on the four perradial tentacles.
The thread-cells of the oral battery develop in the more
proximal parts of the manubrium and make their way through
the endoderm and structureless lamella to the ectoderm of the
mouth region, the movements being effected by the ameceboid
cnidoblasts of the thread-cells. Similarly, the nematocysts of the
perradial tentacles are not formed in situ but probably develop
in the large ocellar bulbs at the bases of the tentacles.
Mr Ruhemann, Action of Urethane on Esters, etc. 181
Action of Urethane on Esters of Organic Acids and Mustard
Oils. By S. Runemann, M.A., Gonville and Caius College, and
J. G. Prrestuey, M.A.
[Read 8 February 1909.]
The sodium-derivative of ethyl carbamate reacts with ethyl
phenylpropiolate not by addition, but with formation of ethyl
phenylpropiolylcarbamate. Similarly the esters of fatty saturated
acids furnish acid derivatives of ethyl carbamate.
Phenyl mustard oil reacts with ethyl sodiocarbamate mainly
according to the equation:
2C,H;NCS, + NaNH.CO,Et = C,;H,,ON,S,Na + C.H,O,
and yields the anhydride of diphenylthiobiuretcarboxylic acid.
Besides this compound, a small quantity of carboxyethylphenyl-
thiocarbamide,
NH (CO,Et) CS. NH.C,H,,
is formed. Analogous is the action of ethyl sodiocarbamate on
other mustard oils,
182 Dr Fenton and Mr Robinson, Homologues of furfural.
Homologues of furfural. By Dr FENTON and F. ROBINSON,
B.A.
[Read 8 February 1909.]
New syntheses have been effected by the application of the
Friedel and Crafts reaction to the halogen derivatives of methyl-
furfural with various hydrocarbons and the results promise a wide
field for further investigation. Improvements have been made in
the mode of formation of the derivatives of methylfurfural and
evidence is brought forward which appears to necessitate a modi-
fication in the generally accepted constitutional ca for the
hydroxy-derivative.
SCONTENTS. 5 =-
PAGE
On a configuration. of twenty-seven “hyper planes mr. Le dimensional
spaces. By Professor W. BURNSIDE ;
~ Note on some double fluorides of sodium. ~ By we A: R. Wiese
(Communicated by Dr FENTON) Se SM asea
An experiment on tonisation with y rays. By L. Vecarp, (Com-
municated by Professor Sir J. J. Tomson) ee ees se
~The absoi “ption spectra of solid tetramethylpicene and a, its solutions.
By J. E. Purvis and Miss A. Homer
The absorption spectra of concentrated and diluted solutions oe orp
By J. E. Purvis. (Plates I—IID) .
The absorption spectra of masvgtene ane- iene By J. E.
PURVIS = : : : : : : : pee eke
On a so-called “sexual” method of forming spores in Raster Be
C. C. DoBELL é : ; Se ce eR a
On the alleged influence of lecithin. Upon the deter mination OF sex tn
rabbits. By R. C. PUNNETT .
~A coloured thio-oxalate. By H. O. JonES a HS. eee
“Observations on the changes in the Common Shore-crab caused by.
Saceulina. By F.A. Ports. (One fig. in Text) ~~ SDARSSES
On the secondary Réntgen radiation from air and ethyl bromide. By
J. A. CrowTHer.. (One fig. in Text) :
A string electrometer. By T. H. Lany. (Five figs. in Text)
Interference fringes with feeble light. By G. I. TayLor. (Communicated
_by Professor Sir J. J. THomson)
On the parametric representation of the coon dineites of writes On & ite
surface in space of four dimensions. By H. W. RicaMonD
The study of discontinuous phenomena. By NorMaN CAMPBELL .
On the nature of anthocyanin. By Miss M. WHELDALE. come
cated by Professor BATESON) .. é : : : ws
The nature of the ionisation produced in a gas by y rays. By R- De <
Krerman. (Communicated by Professor Sur J. J. TEOuOr
(Thvee=fes ine Pex), Seek Se ee gee en
Note onan abnormal pair of appendages wn Lithobius. _ By i: Doe :
CASTER. (Two figs. in Text). . : 2 2 ee
On the migration of the thread-cells se Merisia.. - @elimiany note)
By C. L. BouLENcmR . :
Action of Urethane on Esters of Organie Acids and Mustard ois. By 3
S. RUHEMANN and J. G. PRIESTLEY . Bees
Homologues of furfural. By Dr Fenton and F, RopinsoN .. =.= a
rise
PROCEEDINGS
OF THE
CAMBRIDGE PHILOSOPHICAL
SOCIETY.
ae one rt ee er es ee
|
fom 28 aay Pe eS ae > AME wise
Be PGS eR Ee ee rs Al ;
i fiLUOU Wie a Je pipet
--OF--
} , ~ * -
2 tA ENA § S
: ge | 4
i Sr Be ca eee sa
VOL. XV.— PART -TIE
[Easter Term 1909.]
: Cambridge; -
AT THE UNIVERSITY PRESS,
AND SOLD BY
_ DEIGHTON, BELL & CO, AND BOWES & BOWES, CAMBRIDGE.
CAMBRIDGE UNIVERSITY PRESS,
C. F. CLAY, MANAGER, FETTER LANE, LONDON, E.C.
1909 |
Price Three Shallings
- 19 November, 1909.
NOTICES.
1. Applications for complete sets of the first Seventeen _
Volumes (in Parts) of the Transactions should be made to the
Secretaries of the Society.
2. Separate copies of certain parts of Volumes 1—xt. of f the
Transactions may be had on application to Messrs BowEs &
Bowes or Messrs DEIcHTon, BELL & Co., Cambridge.
-8. Other volumes of the Transactions may be obtained at
the following prices: Vol. x11. £1. 10s. 6d.; Vol. x11. £1. 2s. 6d. ;
Vol. x1v. £1. 17s. 6d. ; Vol. xv. £1. 12s. 6d. ;- Vol. xvi. £1. 10s. 0d. ;
Vol. xvi. £1.28: 6d. Vol. xvi. £3. VsA0d.: Vol’ xix. SF, 3s. 0d
Vol. xx. £1. 10s. Od. ; Vol. xx1. No. 1, 3/-; No. 2, 4/-; Nos. 3 and
4,1/6; Nos. 5 and 6, 3/-; No. 7, 2/-; No. 8, 3/-; No. 9, 1/6.
4. Complete sets of the Proceedings, Volumes 1.—XIV., —
may also be obtained on application to the See of the -
Society. .
5. Letters and Communications for the Society should be
addressed to one of the Secretaries, i
Mr A. E. SHrpuey, Christ’s College. [Biological.]
Dr E. W. Barnss, Trinity College. [Mathematical.]
Mr A. Woop, Emmanuel College. [Physical.]
6. Presents for the Library of the Society should be ad-
dressed to 5
The Philosophical i brary
New Museums,
Cambridge.
7, Authors of papers are informed that the Illustrations and —
Diagrams are executed as far as possible by photographic “process”
work, so drawings should be on a large scale and on smooth white —
Bristol board in Indian ink.
8. Members of the Society are requested to inform the |
Secretaries of any change of address.
PROCEEDINGS
OF THE
Cambridge Philosophical Society.
Some fatigue effects of the cathode in a discharge tube. By
R. WHIDDINGTON, B.A., Hutchinson Research Student of St John’s
College. (Communicated by Professor Sir J. J. Thomson.)
[Read 17 May 1909.]
Skinner’s* experiments on the vacuum tube discharge seem to
suggest that charged hydrogen atoms emitted from the cathode
play a considerable part in the carriage of the current.
Chrisler}+ has studied experimentally the effect of absorbed
gases on the photoelectric activity of metals, coming to the
conclusion that hydrogen again plays a large part in the photo-
electric current. !
The present note describes the results of some simple experi-
ments designed to show what influence the gases occluded in the
cathode have on the emitted cathode rays.
The method employed is qualitative and hardly capable of
quantitative application. It consists of comparing the behaviour
of a cathode, previously treated in various ways, with an exactly
similar, and similarly situated untreated standard electrode, in
the same tube. By this means the complicating influence of
pressure changes was eliminated, for the change over from one
cathode to the other was instantaneous leaving no time for a
change in pressure.
If the looked-for effect has any existence it is reasonable to
suppose that it might be greatest in the case of a charcoal
cathode. For carbon can be made to absorb vast volumes of
many gases.
* Phys. Rev. Vol. xxi. 1905.
+ Phys. Rev, Vol. xxvir. 1908.
VOL. XV. PT. III. iS
184 Mr Whiddington, Some fatigue effects
The first experiments accordingly were made with cocoanut
charcoal electrodes.
Two circular carbon electrodes of equal thickness and about
two centimetres in diameter were mounted symmetrically and
parallel in a vertical straight tube only slightly larger, so as to
face each other at a distance of about 30 centimetres. A sub-
sidiary aluminium electrode was fused in, in a side tube midway
between the two cathodes. Further, each carbon electrode was
arranged so as to be at the geometrical centre of a concave alu-
minium electrode, which, when run as cathode, bombarded its
attendant carbon electrode with an intensely heating beam of
cathode rays.
The upper electrode was taken as the standard. The lower
electrode was heated up by the convergent beam of rays from its
concave cathode, the resulting spot of incandescence being moved
about by means of a bar magnet. After four or five hours’
continuous heating and pumping the carbon ceased to give off
gas, indicated by the width of the Crookes’ dark space remaining
constant.
The spectroscope showed the emitted gas to be mainly oxides
of carbon with a perceptible trace of hydrogen.
The tube now contained an upper electrode full of gas, and a
lower one free of gas. The two electrodes were then connected
direct to the secondary of an induction coil (giving a 6 in. spark).
On making alternately the upper and lower carbon electrodes,
cathode, no difference in the character of the discharge could be
detected. The cathode ray emission as roughly indicated by the
green glass phosphorescence was the same and the Crookes’ dark
space was in both cases of the same width.
Now, on running the lower carbon as cathode for 10 minutes,
the subsidiary side electrode being anode, a further small quantity
of gas was given off indicated by the shrinking in of the dark
space. As before the gas appeared to be oxides of carbon and
hydrogen.
A comparison of this now further depleted lower carbon with
the standard showed a distinct alteration in properties. The
green glass phosphorescence was very much less brilliant and the
Crookes’ dark space narrower and more sharply defined. After
20 minutes running as cathode, this fatigue effect, as it may be
called, became more marked; but after half an hour the cathode
seemed to get into a constant state. The state of affairs can be
summed up in few words by saying that the upper standard
cathode behaved as though the tube were hard, the lower one as
though the tube were soft, yet the gas pressure was the same in
either case.
The fact that the boundary of the Crookes’ dark space
of the cathode in a discharge tube. 185
becomes more sharply defined with time of running, seems to
suggest that the cathode rays emitted by the fresh cathode have
various velocities, but that as the running is continued, the faster
and more penetrating rays cease to be emitted in any quantity,
until at last when the cathode is quite fatigued the rays are very
homogeneous.
Having reduced the lower carbon to this fatigued state
attempts were made to restore it to an equality with the standard.
To this end it was caused to absorb hydrogen, air, carbon dioxide
[and helium] by cooling in liquid air and admitting the gas.
No appreciable return to equality with the standard could be
detected.
It should be mentioned that during the absorbing process the
upper standard carbon electrode was kept hot to prevent any
absorption taking place there. This meant that both oxides of
carbon were being absorbed by the lower electrode during the
admission of carbon dioxide, for carbon monoxide would be con-
tinuously produced by the union of the incandescent upper carbon
with the surrounding carbon dioxide.
Platinum electrodes were next tried, the heating in this case
being produced by the passage of an electric current. No certain
results could be obtained owing to the erratic behaviour of the
platinum after heating. The only point that could definitely be
established was that, as in the case of the carbon, running as
cathode could liberate gas which mere heating could not.
Aluminium electrodes were next tried but without any heating
arrangement. The same fatigue effect though rather less marked
than with carbon was observed. Again it was found impossible
to restore the cathode to the original (standard) state by causing
the metal to absorb various gases. The method of causing gas
absorption in this case was to heat up the metal to about 400° C.
in a glass tube containing the gas required and then allowing it
to cool. In this way some little of the gas was always absorbed.
A considerable volume of hydrogen could be introduced into the
body of the metal in quite a different way. The cathode was made
one of the electrodes in an electrolytic cell containing dilute
sulphuric acid and the current passed so as to deposit hydrogen
against the aluminium. Although this caused considerable
absorption of hydrogen yet the fatigued metal showed no return
to the standard state.
It is well known that the green phosphorescence excited on
glass by cathode rays falls off in intensity as the bombardment is
continued.
This effect was eliminated by using a. horizontal discharge
tube with the electrodes as before facing each other at either end,
in the centre of which was suspended a Willemite screen carrying
13—2
186 Mr Whiddington, Some fatique effects
a little magnet so that the screen could be rotated by an external
magnetic control. The screen was midway between the two
electrodes. When both electrodes were fresh the phosphorescence
of the screen was independent of the cathode from which it
received the exciting cathode rays. When, however, one of the
electrodes was run as cathode for some time, the Willemite glowed
much more vividly when it was responding to rays from the
fresh cathode, the dark space being a centimetre or so in width
and the distance of the screen about 5 cms.
This fact lends support to the view that at any rate some of
the rays emitted from a fresh cathode are faster and therefore
more penetrating than those emitted from a run cathode.
The surface of the aluminium used in the above (and future)
experiments was always polished with the finest emery powder so
as to be sure of always having a constant surface,
It was thought that the observed effects might be merely due
to surface influences. This was proved to be not so, by filing off
about ‘2 mms. of the metallic surface and repolishing. The run
cathode so treated appeared to be still as fatigued as ever.
A fatigued cathode also shows no very marked signs of recovery
if left to itself. In one particular case a tube was left at atmo-
spheric pressure for over three months and at the end of that time
the fatigue effect was still as obvious as it had been immediately
after the running period.
At first, running the fatigued cathode as anode did not appear
to have any effect, but using a very small induction coil (giving
5 mm. spark) to produce the discharge, an effect was observed
when the pressure was between certain limits. When the fatigued
cathode which had been run as anode was made cathode again,
there was a sudden burst, so to speak, of phosphorescence when
the discharge first passed. This sudden brilliance however was
only momentary, lasting but a small fraction of a second. ‘This
transient recovery did not seem to depend on the length of time
the electrode was run as anode; making it anode momentarily
produced as much effect as running for quite a long time. The
effect was most marked in hydrogen but could be got in other
gases as well.
Chrisler in the paper cited quotes figures showing that the
photoelectric current for metals increases enormously if the elec-
trode is run momentarily as anode in hydrogen. ‘This falls into
line with the cathode effect described above, but his further
observation that running as anode in gases other than hydrogen
actually diminished the photoelectric effect finds no counterpart
in these experiments.
It was thought that the volume of metal forming the cathode
might influence the time taken to produce the fatigue effect.
Experiments on this point gave no definite results.
of the cathode in a discharge tube. 187
The direct results of these experiments are:
(i) That an electrode contains gas which cannot be driven
off by an ordinary heating but which is easily evolved when the
electrode is run as a cathode.
(ii) That an electrode after running as cathode for some
time emits more slowly moving and more homogeneous cathode
rays than it does when fresh.
(ii) That it is not possible to restore a “fatigued” ssiinedls to
its original state by causing it to absorb hydrogen, oxygen, nitrogen,
carbon dioxide, carbon monoxide or helium.
It was thought that measurements of the cathode fall of
potential might throw some light on (ii).
The cathode fall was measured only in the case of aluminium
cathodes in air.
A platinum exploring point was used in conjunction with an
Ayrton-Mather electrostatic voltmeter.
The instrument always took from half to three-quarters of a
minute to reach its final reading owing both to the smallness of
the collecting point and the large capacity of the electrometer
quadrants. The arrangement could therefore not be used to
measure rapid variations in the cathode fall.
In most cases the cathode fall started from a low value, rising
rapidly in about three minutes to a maximum and then gradually
falling to a final steady state. No value can be attached to the
first rapid rise to a maximum as very often the time taken was
comparable with the time of lag of the instrument. The value of
the maximum recorded by the electrometer was very variable with
different cathodes, even when they were cut out of the same sheet
of metal. The limits of variation were between 280 and 400
volts. In only one case was the upper limit reached, usually
300 volts was about the value. The final value to which all
cathodes converged was 265 volts and the time taken was of the
magnitude of 10 minutes.
Thus the cathode fall for a new aluminium cathode is rather
greater than for one which has been run some time, the difference
usually being about 20°/, but sometimes being as much as 60 “/..
This is what the qualitative experiments might have led
one to expect; for a new cathode has a wider dark space than
a run one.
The effect of absorbed gases was tried but with negative
results.
Running the cathode as anode also produced no change that
could be detected in the cathode fall. This again is what the
previously described experiment might be taken as predicting ;
for the effect could only be a momentary one and could not be
188 Mr Whiddington, Some fatigue effects of the cathode, ete.
detected owing to the great time lag of the instrument. No
collecting point device could be expected to indicate changes in
potential so rapid as this.
Some quite thin aluminium plate ‘01 cm. thick was tried in
the cathode fall tube. It was found that the cathode fall rose
almost immediately to the final value 265 volts instead of starting
from a high value and then slowly diminishing with time.
This observation suggested that the time taken for a cathode
to give its final value for the cathode fall might depend on the
volume of the cathode, the time being greater, the greater the
mass of metal involved.
Such time effects were looked for but could not be quantita-
tively worked out owing to two main causes, firstly to the fact
that different cathodes did not start from the same high value of
the cathode fall although they all reached the same final value,
and secondly to the fact that even two electrodes of the same
thickness and size cut out of the same sheet of metal and starting
from almost the same high value took very different times to reach
the same final limit.
In general however it seemed certain that for heavy cathodes
a considerable time was required to reach a steady state, while
light cathodes reached it immediately, without any gradual fall.
This result led at once to the trial of very thin cathodes in
the ordinary discharge tube. They did not show any fatigue
effect, the dark space being sharply defined from the commence-
ment.
It is possible that some gas is present in the new metal which
is expelled by running as a cathode which is responsible for these
fatigue effects. If the gas is one of those mentioned above it
certainly cannot be made to enter the material of the cathode in
the ordinary way. On the other hand it may be one of the rarer
gases or even an unknown one.
It is possible that photographic methods using large masses
of metal for the cathode may reveal this gas. But in these
experiments the only gases evolved appeared to be oxides of
carbon and hydrogen.
I have pleasure in thanking Prof. Sir J. J. Thomson for
suggesting the work and for his kind interest while it was being
carried out.
Mr Whiddington, Note on the electrical behanour, etc. 189
Note on the electrical behaviour of fluorescing rodine vapour.
By R. WarpprineTon, B.A., Hutchinson Student of St John’s
College. (Communicated by Prof. Sir J. J. Thomson.)
[Received 4 August 1909. ]
In view of the fact that no satisfactory theory of fluorescence
exists, it was thought likely that a study of the electrical be-
haviour of iodine vapour when fluorescing might give valuable
results.
The apparatus employed consisted of a wide glass tube into
which a cylinder of copper gauze slipped tightly. The light
could be concentrated within the tube through a hole cut in the
auze.
i The electrodes were discs of copper placed parallel and at a
distance of about three centimetres apart. One electrode was
earthed and connected to the gauze sheath, the other being
connected to a sensitive Wilson gold leaf electroscope.
In the first trials ebonite insulation was used, but as the
iodine—which was liberally sprinkled within the vessel—was
found to attack it, quartz was substituted in its stead.
The vessel was connected to a mercury pump and evacuated
to the limit set by the vapour pressure of the iodine (4 mm.
about).
When a beam of arc light was focussed between the electrodes,
the fluorescence was plainly visible but no trace of ionization
could be detected even when the applied electric field was almost
enough to produce a discharge.
To be quite certain that the ionization chamber and electro-
scope were in good working order, a test was made with a weak
sample of radium. Even at this low pressure there was a very
rapid deflection of the gold leaf.
This experiment conclusively shows that ionization is not
necessarily an accompaniment of fluorescence.
190 Mr Sharpe, On the Reflection of Sound at a Paraboloid.
On the Reflection of Sound at a Paraboloid. By the Rev. H. J.
SHARPE, M.A., late Fellow of S. John’s College, Cambridge.
[Received 22 May 1909.]
38. In the year 1899 a Paper by the author with the above
title was published in Vol. x. Part ut. of the Proceedings of the
Cambridge Philosophical Society. That Paper contained some
minor and possibly some major Errata, which I should like some
day to correct, but that is not my object at present. Rather it is
to make an addition to my former Paper suggested by Arts. 10, 18
and 28, in which additional results are obtained, shewing a strange
analogy with the Reflection of a point of Light at plane surfaces.
Thinking it would be better to make this Paper intelligible by ztself,
I have ventured to repeat, as shortly as possible, some of the early
part of the Analysis. Wishing also this Paper to be considered
part of the first, I have made the numbering of the Articles,
Equations, and figures run on continuously.
Fig. 8.
39. Suppose then (fig. 8) ZR to be the material parabolic
Reflector, O its focus and Ow the axis of 2. The sound motion is
supposed to be such that it is everywhere symmetrical round the
axis, and in planes passing through it.
’ Let P be any point within the Paraboloid ZR. Draw two
confocal parabolas PU and PV passing through P with O as
focus. Put OU =5 : OoVv=; and OL=5. Tt will be found that
any sound motion within the Paraboloid must satisty the following
equation
4 (os er dF =) 1 @F
U+v Ue ae du) @ de”
Mr Sharpe, On the Reflection of Sound at a Paraboloid. 191
For sound motion F will be of the form
P sin (2pat) + Q cos (2pat),
where P and Q each satisfy the equation
2 2
ceo (aa t ae ast du) TPP =O.
As in the present Paper we shall only consider stationary
vibration, either P or Q will always be zero. A particular solution
of the last equation is P= UV, where U is a function of w only,
and V of v only, and
av dV
Ura tga TAP OA) Vi Obes ae enciencts: (96),
eu dU
ue + da + (pu+A)U=0............ (97),
where A is an arbitrary constant, pa/m is the frequency and a is
the velocity of sound. It will be found that the condition of
reflection at the paraboloid ZA is that sty should =0 when w=1.
In all that follows it will be found to conduce much to brevity
to use new: independent variables, defined thus
pu=wu, pv=v, pl=l and A/p=A’;
(96) and (97) then become
NEVE Vie, al!
Ona awit Urea) 520 ADC OnC Daoud (98),
waa Uae OF 5 :
UW aah ey Ae +A’) U=0 no3005500007 (99),
from which p has disappeared and the condition of reflection
becomes
dU hes
a =O Wien eee noe (100),
We may now drop the dashes, if in all final results we re-
member to put
pu for u, pv for v, pl for l, and A/p for A.
By this we come back to the original notation.
40, We will first take a comparatively simple case. We will
suppose A =0. This case was partly treated in Arts. 10O—17, but
more will be added. In this case we get V=J,(v) and U=J,,(w),
and the condition of reflection is that dU/du=0 when w=1.
192 Mr Sharpe, On the Reflection of Sound at a Paraboloid.
It is known that the equations J, (w)=0 and = J, (u) =0 have
an infinite number of real roots, so that 7 has an infinite number
of values appropriate to the present solution. The same can be
said of the original pl (Art. 39), and (as we suppose p constant) of
the latus rectum of the Reflector. It will be interesting to find
the various points on the axis where the air-velocity is a maximum,
and especially the position and intensity of the greatest maximum.
We shall suppose the vibration stationary, then it can be shewn
(Art. 5) that the air-velocity in the direction OV (fig. 8) at any
point V on the axis is 2 ae time factor, which = 2 aR J, (v) Xx
time-factor. We shall, however, for brevity always omit the
time factor. The position on the axis to the right of O where
the air-velocity is a maximum is determined by the equation
a? Nee d
Te J, (v) =0, which is the same thing as dy (v) =0.
Now the zeros and turning points of J,(«) are given by the
following Table, where, for simplicity, we have retained only two
places of decimals.
When w= 1°84, 5°33, 854, 11°71, 1486, 18:00, Gc.
Then oF (x) =—J, (#2) =
—'58, +°34, —'27, +°23, -—:20, 4°19, &e,,
and the roots of J, (~)=0 are given by
oO) YSssy COLD Odi. dese. ode:
Looking at fig. 8, if P’ be the optical image of P in OR’, we
see that the w and v of P will be equal to the v and wu of P’
respectively, and when A =0, it will be found (see Art. 5) that
the sound motion to the left of OR’ is the image of the sound motion
to the right of OR’. It follows that if in fig. 8 we draw the parabola
I’R’ the image of LR’, there will be no air-velocity normal to
L'R’; and L’, as well as L, will be a point of rest.
We can now see something as to the nature of the air motion
and sound intensity, at any rate at points along the axis of the
reflector ZR’. ‘To the right of OR’ (see fig. 9) along the axis Ox
we have an infinite series of points 2, 2%, U3, Us, etc., Whose abscissae
are Ov, = 1°84, Ov, = 5°33, ete. The ordinates of the wavy curve
represent the magnitudes and directions of the corresponding
maximum air-velocities.
For instance, at v, the magnitude is ‘58 to the left,
5) ” Vg ” ” “34 ” right,
4 i Vs 4 ‘a 27. , ) /lefivand* sere
1,72) 73) Ts, etc, are intermediate points of rest.
Mr Sharpe, On the Reflection of Sound at a Paraboloid. 193
It will be observed that as we pass from infinity along the axis
from x towards O the maxima air-velocities gradually increase in
intensity till at v, we have the greatest maximum.
On the left of OR’ we have a state of air-velocity at uw, U2, Us, etc.,
Pi, Px, Ps, ete., exactly the image, in the line OR’, of that “hie
exists on the right of OR’. Ofcourse on the right on O v1, U2, U3, etc.,
are real foci of reflection. But on the left of O (as the figure is
drawn) only uw, and w, are real foci, all the rest us, us, etc., are
virtual foci of reflection. And here it must be noted that the
point r, in fig. 9 is supposed to be identical with the point LZ’ in
fig. 8. The points Z and L’ being points of no air-velocity must
be made identical with some of the points 7,, 72, etc., and pj, po, etc.,
Fig. 9.
in fig. 9—taken in pairs as 1p, Topo, VYsp3, etc. As we have
chosen the size of the Reflector so that L’ coincides with 7, (fig. 9)
we shall have / (or, Art. 39, going back to the original notation)
pl=T01. Suppose / to be 8 inches (the size of a portable Sound
Reflector I actually made). Then p=10'51, a high note just
within the range of a piano.
Suppose (fig. 9) we had made L’ to coincide with 7, (instead
of r,) we should have got pl = 3°83, and then p would be 5°74. We
thus see that as we experiment with higher and higher notes,
more and more points of maximum velocity are crowded into the
space LL’ (see fig. 8) that is in the neighbourhood of the focus 0.
It must, however, be noticed that in this case where A = 0, which
we have been considering, O is always a point of rest.
194 Mr Sharpe, On the Reflection of Sound at a Paraboloid.
41. We will next suppose A finite. We have now to use the
equations (98) and (99)—but we will drop the dashes and no
mistake will arise if we are careful to remember the remark at the
end of Art. 39.
In (98) and (99) A is one of the roots of the equation in A
dU /du— (0; whente:—(0\ce 9... tee eee (100).
Suppose, if possible, A, and A, to be two different roots of this
last equation, and when A=A,, A, respectively, let U become
U,, U, respectively. Then
BOR eR CHOR
2 ed ea
CU TU
Chi du tet A») U,=0.
It is easy to shew that
mae (uv. Dye or =) +(¢4,—A,) Ue
du du du
Integrate this with regard to u between the limits 0 and J,
when we get
l
| U,Uidu=0 (101).
0
This shews that the equation (100) considered as an equation in A
has all its roots real, for otherwise, if A, and A, were two conjugate
unreal roots, (101) could not be satisfied.
42, We will next suppose that in (99) wis much larger than
A, then it is evident that, in the neighbourhood of points which
satisfy this condition, U does not differ much from J,(w), and
the curve whose ordinates give dU /du is a wavy or periodic curve
which cuts the axis. This is corroborated by Art. 23, where it is
shewn that if «>A we have approximately
=> cos (U+4$A loguta) woes (102),
u
where B and a are constant functions of A.
~ [N.B. In Art. 23 we have V, v and —A, but it will be found
that exactly similar reasoning may be applied to the case U,
wu and + A.]
We will next suppose that v is much larger than A, then we
can shew in like manner that, near points which satisfy this con-
dition, the curve whose ordinates give dV/dv is a wavy curve
Mr Sharpe, On the Reflection of Sound at a Paraboloid. 195
which cuts the axis, also when »y >A we have approximately from
Art. 23
V=5 cos (v—4 A logu+@) .........055 (103),
v
where B’ and a’ are constant functions of A.
43. We will next suppose that in (99) u is much smaller than
A. Then divide each side of (99) by A and put du=z. We
then get approximately (see Art. 19 of this Paper), if z is large,
cos {2 (Au)? — 4a}
(Aut ! 7 eocccceces
This shews that in the neighbourhood of points which satisfy
the condition u/A small (A being large) the curve whose ordinates
give the velocity dU/du is a wavy curve which cuts the axis.
We will next suppose that in (98) vis much smaller than A.
Proceed as before. Divide by A and put Av=z. We shall then
get approximately (see Art. 20 of this Paper)
U=J, (22) =
Z
V=Z=1+2 + ap
It is evident from this, that in the neighbourhood of points
satisfying the condition v <A (A being large) no positive value of
v can satisfy the condition of dV/dv being a maximum or minimum,
and that therefore near such points the curve, whose ordinates
give dV/dv, is either not a wavy curve at all, or if it 7s a wavy
curve, that it does not cut the axis. This kind of curve is shewn
by the wavy line in fig. 10. Or it is possible, but not likely, that
between O and A the velocities might uniformly increase or
uniformly diminish without there being maxima or minima.
Perhaps we might be allowed to speak of this kind of curve as an
exponential curve. All this is further corroborated by the fact that
when z is large the approximate value of V takes an exponential
form (see Art. 20)
+ git ete. = Su[2(— 2h}
ae Par are d
7 (Avi :
44. We have now examined the shape of the air-velocity
curve in the neighbourhood of four classes of points defined thus
We Ay bw Aly > AN y= A.
It remains to examine the same near four other classes of points
defined thus
u does not differ much from A in excess or defect,
7) or) 33 ” A 7
+P]
196 Mr Sharpe, On the Reflection of Sound at a Parabolord.
We shall take the two last cases first. In (98) put v= Aw and
suppose both v and A large, and « nearly = 1.
And first we shall suppose « < 1, equation (98) then becomes
2V 7
eT Lat ca 5 oignsyeeaee (106).
du
With the above suppositions, a solution (68) is given of this
equation in Art. 26. [It must, however, be admitted that (68)
fails if « be too near 1. For this case and for the case of uw
being actually =1 another solution must be sought.] The solution
(68), however, answers very well if say « is near $. It will be
further observed that the solution (68) is of an exponential
character, so it seems to follow by reasoning similar to that used
before that (for points for which «<1, but v and A both large)
the air-velocity curve is exponential. It is important to observe
that this result agrees very well with the latter part of Art. 43.
. due
45. Next, with the above suppositions, we shall suppose « > 1.
In this case it is better to write the equation for V thus
ev av
eae dye
A solution (70) of this equation is given in Art. 27.
[As before, we must admit that fhis solution fails when yw is
very near 1 or actually =1, but it answers very well if « is near
or = $.] It will be further observed that the solution (70) is of a
trigonometrical or periodic character, so it seems to follow as
before that (for points for which «> 1, but v and A both large) the
air-velocity curve is wavy and cuts the axis. Again it will be
observed that this agrees very well with the latter part of Art. 42.
+-A°V (pn 1) =0 «eee (107).
46. According to the beginning of Art. 44 it would now be
our duty to examine the value of U when wu does not differ much
from dA in excess or defect. In (99) put w= Ap, and suppose u
and A both large, then (99) becomes
aU dU pet ES
ke de + dis +A2U(1+p)=0 «20.0.0. (108).
As ye is supposed nearly = 1 this equation does not differ much
from
7 ad
K = +o 24°U=0.
Put 24%=y. Then
a@U dU
pee ee T=
erate a ae 0.
Mr Sharpe, On the Reflection of Sound at a Paraboloid. 197
Then U =J,(2v2) =J, (22 A p2).
As A is large and p about 1, we get nearly
| _ cos (22A py? — Fr)
(AYE pA
This shews that the air-velocity curve near the points defined
as above is wavy and cuts the axis. It seems probable that this
solution will take the same form whether p differs from 1 in
excess or defect.
47. I will now give a figure (fig. 10) which will illustrate at
one view the chief results arrived at in Arts. 42 to 46. The
figure is of course not drawn to scale. The Numbers 42 (1) etc.
refer to Art. 42, First Part, etc. The little dots close together
near a large point on the axis mean that the air-velocity curve
near the point is wavy, like that in fig. 9, and cuts the axis.
u>A u=A u<A V<Av-A v>A V>A
42 - A 43 943 44 A465 VL 42
(1) 46 (1) (2) (2)
Fig. 10.
In this figure LAOA’ is the axis of the Reflector of which O is
the focus and L the vertex. OA is measured to the left of O=A
and OA’ to the right = A. One curious result is that at all points
between O and A’ on the right of O the velocity curve is
“ exponential.”
198 Mr Robb, Discussion of a difference equation relating to
Discussion of a difference equation relating to the tension of
overhead wires supported by equidistant poles. By A. A. Ross,
M.A., St John’s College.
[Received 22 May 1909.]
Section I. On the Form of the Solution.
When overhead wires are suspended from poles for electrical
purposes, certain precautions must be taken in adjusting the
tensions, since otherwise the snappmg of the wire may lead
to the breakage of a large number of poles.
The mathematical problem thence arising has already been con-
sidered by several writers and among others by Messrs Hawthorne
and Morton in the Philosophical Magazine, Vols. X1. and X11, 1906.
Their result is somewhat vitiated through taking the quantity
denoted by “7” asa constant ; whereas it generally varies through a
wide range (Vol. XI, p. 634).
The attention of the writer was drawn to the problem by
Mr W. H. Logeman who has himself investigated it by a graphi-
cal method which is however quite ditferent from the following.
In practice the wire is stretched between “anchor poles” which
are often long distances apart and may be regarded as rigid; while
between these it is supported by ordinary poles which in normal
circumstances are not subject to transverse stress. When a break
occurs in the wire, the ordinary poles are subject to forces tending
to deflect them and the deflecting force on a pole is equal to the
difference between the horizontal components of the tensions in
the two adjoining sections of wire.
If these forces lie within the limits of safety the deflections of
the poles will be proportional to them and we may assume a con-
stant of proportionality H, such that the horizontal displacement
of the point of attachment of the wire = H (deflecting force).
Let 7,, T., Ts, ... be the horizontal tensions in successive
sections of the wire counting from the break and let Z be the
common distance between successive poles.
If X, be the horizontal displacement of the top of the nth pole
counting from the break, we have
An = H(T,, sox Lp);
Any = A Tra — an).
Thus Ana — An =A (Lav + Tea —2To).
The total distance apart of the extremities of the nth section of the
wire will accordingly be
L == Any — &n = ae He Gore + Ja —2 AN
the tension of overhead wires supported by equidistant poles. 199
We must now make use of a well-known property of the elastic
catenary. (See, for instance, Routh’s Analytical Statics, p. 373.)
Let «# be the horizontal distance of any point of this curve
measured from its lowest point while s, is the unstretched length
of the intervening portion. Let further 7, be the horizontal com-
ponent of the tension ; let w be the natural weight of the material
per unit length and let # be the elastic modulus.
We have then
a2 5 Th og fe, |, we
Bag Oa log te +a/lt+-— -t-
Treating our wire as perfectly flexible we may identify 7), with the
horizontal tension in any section and 2# with the total distance
apart of the extremities, while 2s, will be the natural length of the
portion of wire. We have accordingly
L+ A (Tsi + Tn —2T x)
Se ye A
MN a PES ee
WS,
SU
powers beyond the third (as is permissible if the sag of the wire
be not too great), we get
If we expand this logarithm in powers of neglecting those
4 4 _ 28, w's,?
L+ A (Vy + Dn — 20 n) = Fy Ty, + 28, — 372
4 25,—L Sy S?w?
a Dat Pass =p 42( 14 Grp) To grr
At a great distance from the break the tension in a section will be
practically the same as it was before the break occurred and may
accordingly be denoted by 7,,. Our problem is thus reduced to
solving the above equation subject to the conditions
T, F 0,
Lal
say, where 7 is a finite quantity.
The equation may be written briefly
Toa + Enis = + WT y — Fr
Putting n= we get i
C ray
m7 26-1) T =a.
In order to solve the equation we shall assume that 7, may be
expressed in the form of a series of a particular type and shall
VOL. XV. PT. III. 14
200 Mr Robb, Discussion of a difference equation relating to
afterwards justify the assumption by investigating the convergency
of the series. Let us assume then, if possible, that
C C2 Os
T,=T (1-a7,-&pR-% ER ).
where Qj, @, ds,... Cand K are quantities to be determined.
We have then
C : C2 = Cs
T,1=T(1—a k= Kk — aK Km % Km — ir
Oo Vas Coca, CF
Twn =2(1—$oee— Bi Rm Em)
— 260, = — 22 (1-0 35 Gute oe ii
2 Rm % Rn
—a=2(b-1)T-7,
C
Lele Kn + (8a°+ 2a, js =
Ta Ts)
Gs
+ (4a,° + Gaya, + 2a) Km pees l :
thus E
Prat Dna — 26T;, —a + Tr
i 2c C
sets oj Tp) A at
=—T | {x ~ K 2b m™ Ch
1 2c 3ca,*) C?
Cel age eene OY A ae care Sab sean
ie (x: + 2b 7) a —~ Ths L an
+ l A Ks cand Ts Shr a Ts at? 2) a sn
CG
an equation which determines KX.
The calculation of the successive coefficients (as well as the
value of K itself) may be considerably facilitated by the help of a
table of hyperbolic functions*. In order to do this let us write
he iGree Si 2 /7"s 22
cosh o=b+ m=1 + spe BF + s{w*E)
: Oe ae
and = 278 = GHT
* Good tables of these functions by C. Burrau have recently been published ;
Berlin, 1907. Georg Reimer.
the tension of overhead wires supported by equidistant poles. 201
1 1
Then 5 (x + Zz = cosh o,
and since K must be greater than unity if 7, is to be finite,
we have
K =e".
Further : (x m +. a) = cosh mo,
so that the value of these expressions may be at once obtained by
the use of the tables and considerable calculation thereby avoided.
We then have
a! 6
~ cosh 2a — cosh w
6
~ cosh 3a — cosh w
As 3 a,’,
As (4a,’ + 6a,a2),
ee)
Since cosh mw — cosh @ is always positive, these coefficients will
all be positive if a is so. The value of a, is arbitrary, but the
presence of the constant C enables us to make it unity without
loss of generality. We have therefore
ia
30
db = —-—
> cosh 2@ — cosh w’
2 Cd oe fan 180
U2 cashisa = cosh @ cosh 2m — cosh w|’
Ce
Cr eC
Thus
C 30 C?
y= PN 3 2 — cosh wo kK”
-2 é ie 180 C3 = -
cosh 38m — cosh w os cosh 2m — cosh -) hn ;
Now since 7,=0 we get
BO - E
3 Bs cosh ie
7 “MLS? d pf
~ cosh 3@ — cosh w (4 ti cosh 2m — cosh =| Gs ae a
an equation which determines C. rac
14—2
202 . Mr Robb, Discussion of a difference equation relating to
This equation may be best solved by tracing the curve
30 ;
cosh 2@ — cosh o”
f ( sie ae) P77
~ cosh 3@ — cosh w . a cosh 2a — cosh »
y=1—-a2-
and noting where it cuts the axis of «.
This series changes sign if we substitute first 2 =0 and then
z= 1,s0 that there must be a root between 0 and 1 if it be con-
vergent. Further, since the terms involving # are all of one sign,
there cannot be more than one positive root which must be the
quantity we require.
Having in this way found the value of C, we may find the
tension in the nth section by substituting Kn for .
The corresponding ordinate will then bear to unity the same
ratio that T',, bears to 7.
It may be readily shown that the curve meets the axis of y, so
as to form an angle of 45°, and has an asymptote parallel to that
axis and at a distance from it equal to CK.
the tension of overhead wires supported by equidistant poles. 208
If T be represented by unity we shall have
T, represented by the ordinate at a =,
C
IN, ” ” ” » = R: ;
weer oere reece esecereeeBoeeeseresesce oot eaeeeeeoersrens
PoeresseseaeesceeeereroeeessoereesegeOFeererrors eed
the general form of the curve being that shown in the figure.
It may be proved that
fle cy a5
Won aed SUS
where
Ses wee,
, VY 37? + s2u2h
As a limiting form of the above inequality we have
21
e
or 541384...< C0 <1.
For the safety of the system of poles it is requisite that the
maximum deflecting force should he within a certain limit. This
maximum deflecting force is clearly equal to 7}.
SEcTION II. Investigation of Convergency.
In order to complete our investigation we must examine into
the question of the convergency of the series which we have
obtained. In order to do so we write
20
cosh w — 1
Rouse)
~ 873 + s2wh"
The equations connecting the successive coefficients then
become
Ly
i cosh w — 1 V9
>~ cosh 2 — cosh w 2 an,
eee cosh wm — 1 1 ( PEO Ra
cosh 3@ — cosh w 2
Cee eeesoer esses eoeesarssaseaeesenesessesesetae
ee ee ewe teres se eseseeOeoeseere esse eesaeoesesone
204 Mr Robb, Discussion of a difference equation relating to
Consider now the expression
cosh w — 1
cosh ma — cosh @
We may expand numerator and denominator in powers of @
and the series are always convergent.
Thus
cosh w — 1
cosh me — cosh @
; ery @* z w®
(m — TL) gy + (mt 1) gt dm —Deatt
1 SU hy 6!
- a4 S ry
m ot (mt 1) Fit (mt + met 1 et +
cosh @ — 1 or 1
Thus ————_——__- has the limit —. for @ = 0 and for
cosh ma — cosh @ m—]
@ > 0 it has always a smaller value.
Let y now be kept constant in our series and let @', ae’, ay’, ...
Vas ; ity. r» Gay &,
be the limiting values of the coefficients as @ approaches zero.
We have
a, =@, = 1,
OS
iV he Ee we #e
Qs 19 ST Mie
1 Re ee
a = ———= ¥ (4a,'* + Gay 'ay’).
22 5)
J ~
It is thus clear that the coefficients ay, as, a, ... are respec-
tively less than ay’, ay, ay’...
Now let
— #—...,
the series being convergent when
z|< 4.
We shall write this
v=1—b«— kw — ba —dat—....
the tension of overhead wires supported by equidistant poles.
We have further
Wise!
yy 1—QWw
=1 + Qa + 2? a? + 234 + 2a +
which is also convergent when
Rat ie Lo. 5... (2m — 3)
m!}
and so we may write
a Oh: w+ 4b, 24 ee by e+,
We have, however, on the other hand
= 1+ 2b,» + (Bb)? + 2b.) a? + (4b? + Gib, + 2b,) a +
Equating coefficients we get
= ; 3,”,
2(¢-1)
1 EDS Uy
b, - (4b,? + 60,b.),
2 (73 ss 1)
ee
while b, = 1.
We shall next show that if m > 2
4.6.8...2m
Tee OT eae) aa
We have in the first place
2A, 2.4.6 7
ty Sp bie 2?
] O 8 < 9
als 7 <a
10 U1
9 g’
ed
re ee
2m 2m+1
205
206 Mr Robb, Discussion of a difference equation relating to
Multiplying corresponding sides we get
2 4.6 Seam emt
1.325. ¢ n=) 2
iin 2s Or
40658 2.02mi ee
Ra ea ee
Thus finally
4.6.8...2m i
< m.
1.3.5... (2m — 3)
For m = 2 this inequality becomes an equality.
It follows that ba, OS bk, Bre
are respectively greater than
where Gals
1
/ 9
A = = od.
eC an eae:
7
as
ee et tee es
and vy is less than unity.
A fortiort
bs, bs, by, was
are respectively greater than
Gg, As, Us, --
and therefore for values of
lel<}
the series
y=1—«#-—4,0 —a,% — aa'—...
converges more rapidly than the series
1 1.3, 1.3.5
y=l—-a#-——2-
4 Fn ga
2! eT aad Aerie
If we include terms up to that involving a” the remainder for
this latter series is known to be numerically less than
1.3 35)...0@m a): ae
m+l1!.. 1—22a’
the tension of overhead wires supported by equidistant poles. 207
which is accordingly a superior limit to the error involved if we
neglect the powers of x above the mth in the expansion of y,
provided
<x
We have in fact for such values of
V1—2@<y<(1—2).
If now we take a value of w less than 4 and form the series
TA -—«#—a,27 —a,x°—...)
it will represent some value of the function 7, where, however,
n is unknown and is not necessarily an integer.
We can similarly form the series
a x? x?
id ee ee
which will also converge and will represent T’,,,.
Now T;,, is positive and the series which represents it is
absolutely convergent and therefore its square forms a convergent
series with the same radius of convergency. Now it is known (see
Bromwich’s Theory of Infinite Series, p. 216) that the circle of con-
vergence of the reciprocal of a power-series is either the same as
that of the original series, or else reaches up to the zero of the
1
Te
convergent series, since the absolute value of x does not extend as
far as a zero of the function 7',.
We thus see that
given series which is nearest to the origin. Thus forms a
c
a + 2bT,, =—- [2 aa N+1
n
forms a convergent series in 2.
But this will represent 7’,_, which is accordingly given by our
series and must be absolutely convergent so far at least.
If now it should so happen that 7,_, is positive, we may repeat
this process and
1 : 4 et rs
T3 will give a convergent series in # and
n—1
therefore T,,, is given by a convergent series.
If, however, 7',_, is negative we have passed over a root of the
equation
1l—2#-a,2°—a,2°—...=0,
1
and consequently ie will no longer converge and the series
n—1
will not give 7’, ».
208 Mr Robb, Discussion of a difference equation relating to —
Now the series is continuous within the limits of convergency
and therefore there will be a definite value of z which satisfies this
equation and is the quantity denoted by C.
Thus AC is the radius of the circle of convergence.
Since V1 — 2a < y <(1 —2) for values of a less than } it follows
that 4<C<l.
We have, however, mentioned that
doit ith
Vl—y+1
This result is obtained by considering the series
w=1l-—#—-av2—- ae —
which is the limit of the series
y=1—2— a, 27 —-0;,0 —....
The series for w can readily be shown to satisfy the differential
equation
2 OU 49 r= —2)+2(1—y)w—+
ania imine . wr
A solution of this equation may be obtained in finite form for
the case where
w=1
dw
da
This solution takes the form
and =—1, whenz=0.
9
(Vi-yuh+Vd—yw+ yi (-w)_ Way +l,
(wi + V— 9) w+9}" 4 |
which gives w= 0
4 ——
when 2== |__|,
oy Wl —y+l
and it is clear that
w<y<l
for values of x less than the above*.
Tt follows that
se,
—- Nay Wis <c<1,
Vli-y+l1
* The expansion of w in powers of « must converge up to this point, since there
is no singularity of the function w anywhere nearer to the origin.
the tension of overhead wires supported by equidistant poles. 209
The complicated form of the solution of the differential
equation renders it less convenient than the simple function
vy =V1—22s
for estimating the degree of convergence, although the former
is valid over a greater range and gives a closer approximation.
Concluding Remarks.
In the foregoing investigation we have treated the problem as
a statical one in which an equilibrium condition has been attained.
The extent to which this supposition is permissible will depend
upon the circumstances of the break, and the rate at which energy
is dissipated in the system. If the wire is suddenly cut the nearest
pole will initially be subject to a force equal to 7, but this force
will quickly diminish before it has produced much effect in bending
the pole.
In any case the dynamical problem appears too complicated to
lead to trustworthy results even if the purely mathematical diffi-
culties should be overcome.
Another important point is the actual number of poles which
must be passed over, counting from the break, before the statical
tension 7’, may be practically regarded as equal to 7’, or T.
It is clear that this depends almost entirely on the value of K,
and » will be very large if K is nearly equal to unity.
We may estimate the size of n by considering that — must be
négligible in comparison with unity. If quantities less than e be
regarded as negligible then we must have
é Y
kn <6.
That is ( log velbys :
Dae
log K
It may perhaps be worthy of note that a superior limit to the
value of 7; is given by
1 La ri _ go (ie) - As (sz) - |
=*| Nor Ws
y¥\W1l—y+1 i
where
=
210 Mr Dixon, On a property of summable functions.
On a property of summable functions. By A. C. Dixon, Sce.D.,
Trinity College.
[Recewed 22 March 1909.]
[Read 3 May 1909.]
1. It is a known theorem*, due to de la Vallée-Poussin, that
if f(x) is a limited integrable real function of # in the interval
(— 7, 7) and if
ie 1 pa
w= =| f(a, m=] © cos nt dt,
1 i :
b, = = [ro sin nt dt,
then 4a,?+ > (a,?+ b,”) is a convergent series, whose sum is -
={" (r@peae
It is also known that if a’, ay’,...,0,... are the Fourier con-
stants of a second such function ¢(z), formed from it in the same
manner as Ap, a), ..., 6,,... from f(x), then
4 MA +> (An Gn, + by by’)
is a convergent series, whose sum is
1 [7
im ik F(t) 6 () di.
If we suppose f(x) to be periodic, with period 27, and take
$(x)=f (x+y), we have
Oy, = ={" J (é+ y) cos ntdt
== |" sft)cosn(t—y)dt
= dy cos ny +b, sin ny,
and b,’ = b, cos ny — a, sin ny similarly ;
also Gees
Thus An Gn, + by dy’ = (ay? + b,?) cos ny,
and ={" fof tty) dt = hag? +S (dn? + bx?) COS NY.
—T 1
* For proof and references see Hobson, Functions of a Real Variable, pp. 715-7,
723-5 ; Bécher, Annals of Mathematics, ser. 2, vol. vir. p. 107.
Mr Dixon, On a property of summable functions. 211
This series is uniformly convergent for all real values of y,
and hence its sum is a continuous function of y; putting « for y
we have that
[7 r@se+ayat
is a continuous function of 2, if f(x) is any limited integrable
function, with the period 27r.
The first object of the present note is to give a proof of this
theorem, independent of the Fourier theory.
A special case is that
Lt | sw@sesayade=[" (ropa
a>0 J —7 —7
=| (f+ a}? dt,
from which it follows that
Lt iy (f(t+2)— f(D} dt=0.
vw) J —T
This special case will be proved first, and the more general
theorem then derived from it. The method of proof is applied
to unlimited, as well as to limited, functions, and thus it is possible
to prove de la Vallée-Poussin’s theorem for all cases in which it
has a meaning.
2. Let f(x) be a limited summable function in an interval
(a’, b’) which includes a, 6 as internal points, and let U, L be its
upper and lower boundaries in (a, b). Divide the interval (L, U)
into n— 1 equal parts, at a2, A3... Gp, and let a,=L, a, = U.
Let the set of values of « in (a, b) for which a,_, < f(x) < a, be
ealled e,(r=1, 2... 7).
Enclose e, in a set of intervals A,, not overlapping, and the
complementary set C’(e,) in intervals [,., not overlapping, so that
A,, [', have a common part <a. This can be done, for /(#) is
summable,
Let the intervals of A,, in descending order of length, be
6, 52... and take an integer p, such that
S Si Si Wee GSI, Bom)
m=1
Let ¢€,, denote the part of 6, which is also in I’,.
The similarly formed system of sets and intervals in
(a+, b+), shifted back a distance @, will serve for the function
J (@+9); let them be distinguished in this new position by dashes,
so that 8’, m 18 6,,m in the new position. Of course 0< b’— 6.
212 Mr Dixon, On a property of swummable functions.
Then for any 2 which is common to 6,,, and 6’,,, and which is
not in I, or I”,,
f(a + 0) —f(2)| <(U — L)/(m — 1).
Now the part common to $,,,, and 8m is §;,m—9, and of this
at most 2e,,,, lies in T’, or I”,.
Hence —| f (w + 0) — f (w)| < (U—L)(n-1)
over intervals, H#, which are together
> S 3 (Came =H = 2e;,m)-
71 ant
Pp
Also > = 8y,m > LA, — ne > (b= a) —
T ti a=1
p p
Da Ch 2) Pp Ga eC
m=1 Tr m=1
The sum of the intervals # is therefore within
n(e+2a)+ npé
of the length of the whole interval (a, b).
Again, | f (a+ @)—f(#)| can nowhere exceed U — L.
Hence I | f (a+ 0)—f («)}? dx does not exceed:
as L
5) @-a)+(U- Ly {n (e + 2a) + np 6},
the first term arising from 4, and the second from the rest* of
(a, 6).
: 1
Here we may give n any fixed value, and put a= eae» 80
fixing p; , the whole will be <= of a quantity
independent of m, and will tend to zero as n is increased.
;
Hence Lt | {f(w+6)—f(2)}dx=0, when fe) is any limited
6>0- a
summable function.
The same method shews that
[fe +0 -F@)|0 de
* Here, as in § 4 below, such end-points of the intervals constituting e, ,, as
lie within 6, ,, form an enumerable set, whose measure is zero, so that it does
not matter whether they are included, excluded, or counted twice over.
Mr Dixon, On a property of summable functions. 213
tends to zero with 0, if g is any positive number, and that the
same is true of
[[Fis@+6)-7)| de
where Fx is any function that is finite when # is finite and
tends to zero with 2.
3. To prove that
I Cay eee
say $ (2), is continuous, if (a, b), (a +2, b+) are both included
in (a, 0’), we have
s@-ow=[ FO (Fe +o—Fe+ Mae
and therefore
b b
[s@-senrs[ (fora | fe+—)—se+ peas
in which the first factor is finite, and the second tends to zero with
x — y by what has been proved.
Hence $(x)—¢(y) tends to zero with «—y, and ¢(z) is a
continuous function of 2.
If we now put a=—7, b=7 and suppose f(x) to have the
period 27r, it is easy to find the Fourier expansion of ¢ (2).
First, ¢ (#) is an even function of z.
Secondly *,
[7 ¢ @) cos ned =[" [" £Of+2)c0s nedtde
=|" [° f@FW) cos n (y —t) dydt
= | . f(t) cos ntdt x | . f(y) cos nydy
+[" £0 sin ntdt x [Fo sin ny dy.
Hence the Fourier constants of ¢ (a) are
Ta,, w(a?+b2), m(a2+ 0,2), ...
0, Ops.
* Tn calculating : | Jt (t+x) f(t) cos nx dtd, we first change the order of
bie
integration, and this is justified for f(x) and f(x+y) are both summable in any
rectangle in the zy plane: the set for which k>/(«)>Z/ consists of lines parallel to
the y axis and the set for which k>f (x+y)>1U of lines which make equal intercepts
on the axes.
214 Mr Dixon, On a property of summable functions.
if those of f(a) are
QQ, ay, gy wey
b, > b., 6 ae
Since ae + & (An? + by?) < a f(a) dx
1 Tr
for all values of n, the Fourier series is absolutely and uniformly
convergent, and since ¢(#) is continuous, the sum of the series is
equal to (x), that is,
(x) = $7ra,.2+ = (Ay? + by”) cos nx.
1
(Hobson, F. R. V., p. 713.)
4, Suppose now that f(z) is not a limited function, but is
still summable in an interval (a’, 0’), which includes a, 6 as
internal points. It will be proved that
[f@+-F@pae
b
tends to zero with 6, it | { f (x)}? dx exists.
Take a finite quantity h, which will afterwards be made to
diminish without limit. Let e,(r=0, +1, +2...) denote the set
of points in (a, b) where (r—1)h< f(a) <rh.
Take a whole number n, so that i { f (a) dx, taken over the
set complementary to @»+...+@+@+.-..-+€n, 18S <¥.
Enclose e, in a set of intervals A,, not overlapping, and C(e,)
in intervals I’, not overlapping, so that A,, [, have a common
part not exceeding a/(2r+1)% The sum of these common parts
for all values of 7 is then < 3a. Then we shall have
A, +A,+...+An
+A_,+...+4_,>(6-—a)— £8, where B=y/n?h2
Let the intervals of A,, in descending order of length, be
5, Om... and take a whole number p, such that
D
> 5;,m >A,—€ (r=0, +1, eee +n).
m=1
Let ¢€,,m be the part of 6,» which is also in T,, and let the
dash again indicate a displacement 9 to the left.
Then for any # which is common to 6, and 8, and is not
in eon ee
If (@ + 8) — f(z) | <b,
Mr Dinon, On a property of summable functions. 215
and as before |f(v+0)—f(x)|<h over intervals H which are
together
ee FO, n=O 2 2e)
1
In this expression 226,,m > ZA,—(2n+1)e
>(b—a)—B—-(2n+l)e,
ZDer,m < 3a,
and the intervals # fall short by less than
B+(2n+1)e+6a+ p(2n+1)0
of the whole interval (a, b).
The value of
a (f(@+ 6) —f (a) de <(b—a) #.
For the rest of (a, b) we have
[if@+o-fe@jtde <2 |{toyrde+2[{f@+ oy de,
To the first term of this, the set where | f (x)| > nh contributes
a quantity < 2y, and the rest a quantity
< 2n?h? {B+ (2n+1)e+6a+ p(2n+4+1)6};
treating the other term similarly, and putting y for n’h?8, we have
b
[ (Fe@+0)-Fw)jtde < (b= a) e+ 8y
+ 4n?h? {(2n + 1)€4+ 62+ p(2n +1) Of.
b
Since now | { f (a)? da
a
exists we may take y=/?, thus fixing n.
We can also take a= a za
ni n
the latter condition fixing p. Then if 0< =. the whole is less
than a certain constant multiple of h?, and can be made as small
as we please by diminishing h.
b b
Baus) Lit (Ff (a'+ 0)— f(a)}? de =0, if | { f(a)}? da
6>0/ 4 a
exists, f(x) being a function which is summable in an interval
(a’, 6’) which includes (a, 5).
VOL. XV. PT. III. 15
216 Mr Dixon, On a property of summable functions.
The same method enables us to prove that
Lt [ \f@+0)-F@)|de=0 if | |F@)| de
exists, by means of “he inequality
IF@+A)—F(@)|<|F(@)|+|F@+ 4).
5. The deduction of the continuity of
[rernsrod
and that of the Fourier expansion for it, still hold good, and in
particular it follows that the series $a) + %(a,?+ 0,2) converges
to the sum
bt aha
=[" {f@pde
even when f(x) is unlimited, if this last integral earsts and ts
Finite.
6. It follows from the results of § 2 that a necessary condition
for a limited function #(x) to be summable is that the superior*
integral of f(v+6)—f(x)| tend to zero with @ The question
is at once suggested whether this condition is sufficient, and if not
whether a satisfactory definition can be given for the integral of a
function which satisfies this condition, but is not assumed to be
summable.
* In Lebesgue’s sense, see Hobson, F. R. V. p. 577.
Mr Orange, On certain phenomena of the kathode region. 217
On certain phenomena of the kathode region. By J. A. ORANGE,
B.A., Major Scholar of Trinity College. [Communicated by
Professor Sir J. J. Thomson.]
[Read 17 May 1909.]
(PLates ITV—IX.)
In the discharge through rarefied gases, the appearances
surrounding the kathode seem to be quite independent of the
form and situation of the anode, and also of the shape of the
containing vessel, provided that the latter does not approach too
near to the kathode. For instance, if one arranges any kind of
kathode, of linear dimensions up to about 4 cms., in the middle
of a glass bulb of about 10 cms. diameter, the various luminous
effects associated with the kathode and known as glows and rays
(together with the secondary effect of phosphorescence on the
walls of the vessel) appear to have no relation to the position of
the side tube which contains the anode, but are determined solely
by the characteristics of the kathode, the intensity of the discharge,
and the pressure of the gas through which it passes.
Throughout the whole range of what are termed low pressures
(pressures less than 1 mm. of mercury, say) the surface of demar-
cation between the Crookes’ dark space and the negative glow is
one of the most conspicuous features of the region and, moreover,
its form is of considerable theoretical interest. The rays which
have been observed in the neighbourhood of the kathode fall into
two classes, the first, which is now fairly well defined, consisting of
the kathode rays, rays that are twisted readily by the application
of a weak magnetic field, while the second consists of a number
of rather indefinite radiations to which Goldstein* has applied the
name of ‘The Canal Ray Group.’
Both classes of rays are in a sense more difficult of treatment
than the glows and dark spaces, for there is no one characteristic
by which a radiation may be apprehended, throughout the whole
range of pressures at which it undoubtedly exists. For example,
kathode rays have a maximum of luminosity at a certain pressure.
If the exhaustion is carried further the rays gradually become less
luminous, but at the same time another property is coming into
evidence, namely, the power of producing phosphorescence on the
glass, until finally we have quite invisible rays manifested solely
by the vivid phosphorescence at their termination. The canal
ray group shows luminosity within a still more restricted range of
pressure and gives rise to much inferior phosphorescent effects.
By piecing together the rather fragmentary evidences of the
* E. Goldstein, Verhandl. d. D. Physik. Gesellsch. (iv), p. 228, 1902; Phil. Mag.
March 1908, p. 372. e ,
15—2
218 Mr Orange, On certain phenomena of the kathode region.
various rays it is possible, nevertheless, to map out their courses
with considerable precision.
Much of the work on the distribution of the kathode rays has
been performed by Goldstein. His paper, “Ueber den Einfluss
der Kathodenform auf die Vertheilung des Phosphorescenzlichtes
Geissler-’scher Réhren”* deals very thoroughly with the phos-
phorescent patterns produced on the glass walls of discharge-
tubes by kathode rays arising from concave kathodes of various
geometrical outlines.
Somewhat related to the same subject was the work of
Campbell Swinton} on the kathode rays from concave carbon
kathodes.
A much more recent paper by Goldsteint deals with the
phenomena of the double or sandwich kathode, while supple-
mentary observations have been made by Kunz.
The subject has also been treated in a rather different way by
Prof. J. J. Thomson||.
The general method in most of this previous work seems to
have been to obtain phosphorescent effects and to establish the
paths of the rays from these. The experiments described below
were intended to demonstrate the paths as far as possible directly
by virtue of the luminosity of the rays themselves.
The primary object of these experiments was to test the view
put forward by Prof. J. J. Thomson of the beams of rays obtained
with a double kathode composed of equilateral triangles. He
observed that well-marked pencils of kathode rays arose from the
middle points of the sides of the triangles, while minor ones
proceeded from the corners. His explanation was that the rays
will occur principally in the regions where the lines of force are
straight or nearly straight, since in such circumstances any positive
ions produced by the kathode rays will strike the kathode very
near the source of those rays, which would not be the case in
regions of strongly curved lines of force.
In my first experiment I employed a double triangular kathode
of extremely unsymmetrical outline, the lengths of the sides of
the triangles being 36, 24 and 16 mm., ie. a:b=b:¢c=3: 2.
It was thought that with this arrangement the straight lines of
force would occur, not at the middle points of the sides, but at
other points which could be determined roughly. Since, however,
the field is due not only to the charged kathode but also to a
large extent to the distribution of charge throughout the region,
* HK. Goldstein, Wied. Ann. xv. 1882, p. 254.
+ A. A. Campbell Swinton, Proc. Roy. Soc. Vol. uxt. (1897), No. 370, p. 79.
+ E. Goldstein, Phil. Mag. March 1908, p. 372.
§ J. Kunz, Phil. Mag. July 1908, p. 161.
\| J. J. Thomson, Phil. Mag. Oct. 1908, p. 657.
4] Ibid. p. 666.
Mr Orange, On certain phenomena of the kathode region. 219
the question is more complicated than at first sight appears. For
other reasons the experiment failed with regard to the primary
object, as will appear in the following account.
Fig. 1.
Experiment I.
The discharge vessel employed was of the form shown in Fig. 1.
It was in continuous connection with a Toepler pump to which the
usual phosphorus pentoxide bulb was attached. The gas used
was generally air* but for a special purpose hydrogen was introduced
* At times apparatus was used in which many joints, made air-tight by the use
of sealing wax and varnish, occurred, and in consequence the gas was largely
carbon monoxide.
220 Mr Orange, On certain phenomena of the kathode region.
at a later stage; this was attamed by having a small bulb con-
taining dry sodium formate in connection with the apparatus and
heating to 250° C. when the hydrogen was required.
The kathode is shown separately in Fig. 2; it was made of
aluminium and carried on a lead of the same material protected
by a glass tube.
An induction-coil with the common interrupter maintained the
discharge and in the usual way a condenser was connected to the
interrupter, but + was found necessary (with the higher gas
pressures at least) to insert a “point and plane’ spark gap im the
secondary circuit, to secure freedom from reversals.
VILILLILILLLLAAALALALLLAMLLLILLMA MMMM LLLL
LLLALALIANLALALALAA REMAN AMMA MMA AA A bcbadeche
Fig. 2
At first it was thought that sufficiently accurate records of the
appearance of the discharge could be obtained by sketching, but
owing to the glare this was painful to the eyes and did not give
very satisfactory results. Recourse was then had to photography
and as a rule little difficulty was encountered. The camera
employed could be extended considerably and consequently could
be set up very near to the discharge-tube, so that photographs
were obtained of nearly natural size. Using Imperial Ortho
plates, exposures of from 2 to 5 minutes were given, the aperture
being 39°
Fig. 1, Pl. [1V*, shows the peculiar appearance of the kathode
region when the Crookes’ dark space envelopes only the corners of
the triangle. [Cp. Kunz, loc. cit. Fig. 16.]
* It should be noted that certain features of these photographs are quite acci-
dental, being reflections from the glass discharge vessel, e.g. the eye-shaped patch
of licht opposite the shortest side of the triangle, and two rectilinear markings
opposite the side of intermediate length.
Further, the positive column, which extends a variable distance down into the
bulb, should be clearly distinguished.
Mr Orange, On certain phenomena of the kathode region. 221
This would indicate that at this pressure the discharge is
taking place almost entirely from the corners of the kathode, the
probable explanation being that the electrostatic field at this
stage is somewhat similar to the simple field due to a charged
triangular conductor. If this is so, those portions of the sides of
the kathode which are free from dark space will correspond very
well with the regions of weakest electric intensity. But these
regions of low intensity are the places where the lines of force are
straightest. Hence, when the mean free path in the gas is suffi-
ciently great for the untrammelled formation of kathode rays, the
discharge will tend to occur to a greater extent than previously
from those parts (according to Prof. Thomson’s view given above),
and the Crookes’ dark space will surround the whole triangle,
although it will be somewhat narrower opposite these places.
[es. ctr, Figs. 1 and 2, Pl. IV.]
In the next photograph, Fig. 2, Pl. IV, the pressure is a little
lower and the kathode rays have become visible. They appear to
come off from practically the whole lengths of the sides of the
triangle, and show maxima of luminosity at certain places. It
seems only too probable, however, that the three connecting pins,
the ends of which appear in the photograph, play a large part in
determining the positions of these maxima. Notice in this and
the following photograph, Fig. 1, Pl. V, the dimpled boundary of the
Crookes’ dark space opposite each of the three sides of the triangle,
as referred to above.
The next photograph, Fig. 2, Pl. V, has a very vague appearance
because at this stage the kathode rays, although now past their
maximum of brightness, are still fairly active photographically,
by virtue of their bluish colour, whereas the canal rays, in spite
of their prominence visually, are inadequately recorded by the
camera owing to their reddish colour. We thus have a medley of
two kinds of rays which it would be difficult and unprofitable to
unravel at this stage. The beginning of the green phosphorescence
due to kathode rays is visible in this photograph in three patches
corresponding to the three sides of the triangle, but the next view,
Fig. 1, Pl. VI, associated with an increased exhaustion, shows the
phosphorescence very well. The blaze of light which masks the
kathode in this case, represents the phosphorescence on the glass
wall nearest to the camera. The actual space within the vessel is
almost free from luminosity, but it is still possible to make out
the boundary of the Crookes’ dark space and a few traces of the
rays.
, The last photograph of this set, Fig. 2, Pl. VI, is certainly the
most interesting owing to the distinct appearance of the ‘canal
rays’ [so-called by Goldstein*]. It corresponds very nearly to
* H. Goldstein, Phil. Mag. March 1908, p. 378.
222 Mr Orange, On certain phenomena of the kathode region.
Fig. 2, Pl. V, but hydrogen was used instead of air in order to
obtain canal rays of a more reddish colour than those in air;
further, a yellow glass screen, which cut out the blue end of the
spectrum, was used in conjunction with orthochromatic plates.
It should be remembered that the kathode rays are still just
visible at this stage, as shown in Fig. 2, Pl. V, but are suppressed
in the present example owing to the photographic method used.
[An exposure of 40 minutes was necessary and this gave rise to
Fig. 3.
difficulties at first owing to the strong tendency of the vacuum to
‘harden’ with continued running of the discharge. By judiciously
fixing the initial pressure of the gas, however, it is possible to
obtain steady conditions if the discharge is given a preliminary
run. |
The configuration of the canal rays can be made clearer by
means of a diagram, Fig. 3*. As the pressure is reduced still
* Tt may be stated here that subsequent experiments have shown that the three
connecting pins do not affect the boundaries of these beams.
Mr Orange, On certain phenomena of the kathode region. 223
further, the rays extend through a smaller distance from the
kathode; the boundaries of the beams also change gradually, so
that at some distance from the kathode the beams become more
constricted.
In previous work, kathodes of symmetrical or nearly sym-
metrical outline have been used, and consequently what one might
call the roots of the beams of canal rays have been hidden by the
kathode. The shape of these has however been inferred from
markings which are found on the inner surfaces of the kathode,
after the discharge has been running for some time*. [Vide Fig. 4,
taken from Goldstein’s paper.] The case described above indicates
that the boundaries of the beams are similar in character whether
they fall within the outline of the kathode or not.
Fig. 4.
But, arguing from the cases of more regular kathodes, Gold-
stein, Joc. cit., and Kunz+ have advanced an explanation of the
curved boundaries which only holds when the curvature occurs
within the kathodic interspace. .
Goldstein says, “ From the concave boundary of the traces and
of the pencils themselves, it may be inferred that the rays pro-
ceeding from any side are subject to an attraction due to the
neighbouring sides. We may, for example, imagine that in the
case of the square the rays are originally convergent along straight
lines, somewhat after the fashion indicated by the dotted lines in
Fig. 7 [Fig. 4 of the present paper], and that it is in consequence
of the attraction exerted on them by the adjacent sides that they
assume the actually observed form (shown by the full lines).”
* EH. Goldstein, loc. cit. p. 377.
+ J. Kunz, Phil. Mag. July 1908, p. 180.
224 Mr Orange, On certain phenomena of the kathode region.
It would seem now that no such simple explanation based on
the geometry of the kathode will suffice. Each beam is sym-
metrical about the central normal to the corresponding side of the
triangle, although the two corners which bound that side differ
considerably. ‘Thus we cannot invoke the aid of the electrostatic
field; this is shown also by the way in which the two narrower
beams cross each other, at a of Fig. 3, as if operated quite inde-
pendently. The latter fact is also opposed to the supposition that
the constituent particles of the beams are strongly mutually
repulsive, a supposition that might have been advanced to account
for the curved boundaries.
The author puts forward the suggestion that the latter are
similar to caustic curves, that is, are the envelopes of straight rays,
as shown diagrammatically in Fig. 5.
We thus avoid the necessity for supposing the beams to be
acted on by peculiar systems of forces, systems which would seem
Mr Orange, On certain phenomena of the kathode region. 225
almost impossible. If, then, we consider the beams to be con-
stituted of straight rays instead of curved ones, the problems
which face us are two much simpler ones.
(i) To account for the directions of the constituent straight
rays, and
(ii) To account for the occurrence of the luminosity of the
rays after, and only after, they have passed through the kathodic
interspace.
With regard to the first question, let us consider the canal
beam which arises from the longest side of the triangle and
runs towards the left of the picture (Fig. 2, Pl. VI).
Adopting Prof. Thomson’s explanation of the mutual inter-
dependence of kathode and canal rays, we suppose this beam to
have its origin in the region to the right of the kathode. It would
be interesting then to know where the kathode rays which, starting
from the longest side of the triangle, run to the right, accomplish
the ionization which gives rise to the canal rays.
Reference to Fig. 1, Pl. VI, tells us roughly where the kathode
rays in question excite phosphorescence on the glass vessel. This
has been indicated by the dotted lime fg in the diagram, Fig. 3.
There is thus at least a rough correspondence between the region
where ions are produced by the kathode rays and the backward
prolongation of the visible canal rays. The same argument
seems to apply to the other two canal ray beams. (It is evident
however, that one limit of the phosphorescence, at e, Fig. 3, is
rendered uncertain by the occurrence of the anode side tube at
that part of the bulb.)
The second question, that of the luminosity of the canal rays
after passing the kathode, remains to be considered. If the canal
rays be regarded as positive ions which move up to the kathode
with continually increasing velocity and, after passing the kathode,
lose their velocity by the reverse process, it is indeed difficult to
account for their luminosity occurring only after passing the
kathode. It can be shown quite readily, however, that the posi-
tive ions are much more likely to be neutralized when moving
away from the kathode than when approaching it. For in the
former case they encounter negative ions moving in nearly the
same direction, while in the latter they encounter them travelling
in nearly the opposite one. Thus if recombination is associated
with luminosity, as is probable, we can see why the canal rays are
visible only after passing the kathode. We may consider the
recombination to occur entirely within a short distance of the
kathode, in which case the visible length of the rays can be
explained by supposing the ions to vibrate for about 5 x 10-* sec.,
or we may consider that recombination occurs throughout the
whole visible length of the beam.
226 Mr Orange, On certain phenomena of the kathode region.
The former view seems better as yet, because
(1) the luminous beams do not seem to be under the influence
of the electrostatic field, and
(2) Kunz* states that “Prof. J. J. Thomson, who applied a
very strong (magnetic) field to these rays, could find so far no
deflexion at all.” (The rays referred to were obtained with an
equilateral triangular double kathode.)
It was next proposed to devise apparatus in which the two
kathode plates were not connected by pins, but carried on separate
leads, and since we did not know definitely by what amount the
plates should be separated, to secure the best results, it was
decided that this should be susceptible of adjustment while the
discharge was running.
Experiment IT.
The apparatus is represented in Fig. 6. One anode A and one
kathode B are supported from above while the other kathode C
and the anode D, which are mechanically connected by ebonite, £,
can be moved up and down by means of a barometer column with
moveable reservoir. (The float H, which is used in this process,
makes contact between the kathode lead and the mercury of the
column. ‘The anode lead is attached to the fine spiral of wire G,
so that it is readily moveable.)
The kathode plates were similar to those used in the first ex-
periment but were bevelled as shown in the figure, with the object
of simplifying the section of the kathodes and hence of the elec-
trostatic field. The two plates, or rather their connections, were
joined externally by a wire. The two anodes were used in de-
termining whether the kathode region were quite independent of
the situation of the anode. On observing that this was so, the
lower anode was disconnected and the upper one alone was em-
ployed throughout.
Although it was possible to obtain views of the kathode region
similar to those of the first experiment, photography in this
direction, i.e. vertically downwards, was out of the question owing
to the inconvenience of the arrangements. It could be seen, how-
ever, that the canal rays formed beams very similar to those
obtained with the original double kathode.
The canal rays are most conspicuous when the separation of
the plates is about 3 mm., but they are observed quite easily with
separations of from 1 to 15mm. With the larger degrees of
separation the beams are more convergent than those described in
Expt. I.
* J. Kunz, loc, cit. p. 177.
Mr Orange, On certain phenomena of the kathode region. 227
Fig. 6.
The apparatus is shown in two parts, the upper one lying to the left.
228 Mr Orange, On certain phenomena of the kathode region.
The inconvenience of the apparatus in the respect mentioned
above was amply compensated for by the ease with which the
region could be viewed in other directions (that is to say, in hori-
zontal directions). Of the appearance in one of these directions,
viz. that showing the kathodes lengthwise, there is little to say.
Fig. 6, Plate 1X, shows the one stage of any interest; the form of
the Crookes’ dark spaces in the kathodic interspace is peculiar,
but it seems to be quite in accordance with the views previously
stated.
Examination of the region in the remaining principal direction
revealed much more interesting features (Pls. VII and VIII), and
what follows refers entirely to appearances viewed in this way. (i.e.
by looking horizontally so that the line of sight is parallel to the
longest sides of the kathodes, these longest sides lying to the left,
while the obtuse angles of course fall on the right.)
The photographs cited are selected from a large number of
records taken. In Figs. 2 and 7, Pl. VIII, the positive column in-
trudes but does not seriously mar the view; it would appear to have
no direct connection with the phenomena discussed in this paper.
The Crookes’ dark spaces are in all cases clearly defined, and it is
noticeable that while they are still unfused, as in Figs. 1, 2 and 6,
Pl. VII, the thickness of the dark space is greater opposite the
remote faces of the kathodes than it is over the interfaces.
The striking feature, however, in most of this series, is the
distribution of kathode rays in the form of a very sharply-defined
cross of St Andrew’s. The pencils are especially well defined on
the left side, that is in connection with the longest sides of the
triangles. On the right some slight confusion occurs owing to the
way in which this part of the triangle is viewed. The system of
rays really forms two sheets, somewhat like slightly truncated
pyramids, the base of the lower one being visible at the lowest
pressures as a phosphorescent trace which encircles the bulb like
a line of latitude (Figs. 2 and 7, Pl. VIII). The pencils are
remarkably restricted transversely at the lower pressures, e.g.
Fig. 7, and, moreover, they pursue a slightly curved path. In
all cases where the two Crookes’ dark spaces either adjoin each
other or are fused together, kathode rays are also emitted abun-
dantly along the median plane of the interkathodic space, e.g.
hie. el vae
I think we may correlate the oblique rays with a phenomenon
described by Kunz*. Kunz used as kathode a hollow cylinder and
observed on the containing vessel phosphorescent rings opposite
the mouths of the cylinder. If the rays described above correspond
to those producing Kunz’s rings, then the latter’s explanation
of the phenomenon must be wrong, as a reference to his diagram +
will show.
* J. Kunz, loc. cit. pp. 164 et seq. t+ Ibid. p. 170.
Mr Orange, On certain phenomena of the kathode region. 229
The way in which the pencils change with the gas pressure and
the separation of the plates is easily summarized qualitatively :
The inclination of the rays to the plane of either kathode
(1) increases with the distance separating the plates, and
(2) increases with the pressure.
There is a transition at a certain stage of exhaustion; at the
higher pressures the rays being sharply bounded on one side only,
while at lower pressures they form true sheets which are well-
defined on both sides.
[Figs. 1 and 6, Pl. VII, Fig. 3, Pl. VIII are typical of higher pressures,
by 21am, i. . » >, rather lower ,,
us 3 rs is » » transitional ,,
i 4 i. a i000 Seostillewerl ,,
5 ie Bae Os Pl V EL ares sia; oad low ]
Figs. 4 and 5, Pl. VII are prints from a single negative. The first
shows details of the rays near the kathodes very well while the
second shows up the general appearance. At this stage the two
“oblique” beams on the left as well as the median beam are
practically horizontal.
In seeking an explanation of the pencils, let us first disregard
the origin of the rays and consider only their directions and
curvature. If we except the comparatively high pressures—at
which the rays are ill-defined—it may be observed that the
asymptotes of the rays always pass approximately through the
central point of the kathode interspace. This would imply that
the electrostatic field is determined largely by the existence of
free charge in the region containing the kathodes, as distinct
from the charge on the kathodes themselves, and, in fact, that
in the cases considered there is a region of negative charge
corresponding roughly with the brightly luminous part of the
interspace.
It has been shown by various workers that the electric intensity
in the ordinary Crookes’ dark space is considerable at all points
but increases rapidly as the kathode is approached; Schuster’s*
experiments indicate that there is a distribution of free positive elec-
tricity in the dark space, such that the volume density decreases
in geometrical progression as the distance from the kathode
increases in arithmetical progression ft.
In such circumstances, the kathode rays in their progress away
from the kathode will acquire a high velocity in the initial stages
of their motion, and subsequently will be affected but little by the
weaker electrostatic fields which they traverse.
Consider the rays from the opposed faces of the two kathodes
in our experiment. The rays from each must in due course enter
* Schuster, Proc. Roy. Soc. xuvit. p. 526, 1890.
+ J.J. Thomson, Conduction through Gases, 2nd ed. p. 541.
230 Mr Orange, On certain phenomena of the kathode region.
the dark space of the other. The particles will lose kinetic
energy as they approach the second kathode, most of the loss
occurring very near the latter owing to the character of the field,
and they will tend to drift a little in the direction parallel to the
kathodes. They will not quite reach the second kathode since
they must have lost some energy by ionization en route; they
may subsequently travel back towards the kathode of origin and
continue to swing across the interkathodic space, but always
trending laterally outwards. Finally, they will have travelled to
the right or left considerably and when their velocity is a minimum,
i.e. when near one of the kathodes, they will be borne out of the
interspace in a manner determined by the electrostatic field.
As was stated above, the visible paths of the pencils indicate
the presence of free negative charge in the middle of the inter-
space, a view which can be supported as follows:
For two reasons there is much ionization (and hence lumin-
osity) in the interspace.
(1) The kathode rays are not as swift here as elsewhere
(since they start in the weaker field evidenced by the thickness of
the dark space), and
(2) the kathode rays, and also some proportion of the
negative ions to which they give rise, oscillate about the median
plane, so that at any instant there is an exceptionally large amount
of ionization proceeding.
The concentration of negative ions must be high in the neigh-
bourhood of the median plane and many of them doubtless travel
out along that plane and constitute the horizontal sheet of rays
seen in the photographs.
In summary then:
We regard the electrostatic field as being due mainly to three
things.
(i) The actual charge on the kathodes; the effect of this
cannot be great, since the covered supports of the kathodes produce
little or no visible effect.
(2) The distribution of positive charge so that it is
especially abundant very near to the surfaces of the kathodes, as
assumed from Schuster’s experiments. (Joc. cit.)
(3) An accumulation of negative charge about the median
plane of the interspace. This must be postulated, I think, to
account for the considerable divergence of the oblique ray sheets
and their peculiar curvature.
The oblique sheets are regarded as the kathode rays arising
primarily from the kathodic interfaces and losing energy by
ionization of the gas as they travel backwards and forwards
between the kathodes. As long as the particles, in their surgings,
Mr Orange, On certain phenomena of the kathode region. 231
arrive within close range of the kathodes, they will reverse their
paths in such a powerful field that they will gain sufficient impetus
to travel in a fairly direct line towards the other kathode.. When
they have lost so much energy that they fail to reach the high
intensity zone at the end of one of their oscillations, they will be
dominated much more by the influence of the postulated region
of negative charge at the centre of the system, and will be repelled
_ out to form the oblique sheets.
The difference between the sheets at the higher and lower
pressures can be explained simply thus: At the stage shown in
Fig. 1, Pl. VII, the kathode rays produced at the interfaces will
lose much energy in crossing over (because of the higher gas
pressure chiefly).
Consequently the rays when they start out laterally will be at
various distances from the kathode; that is, they will have lost
very different amounts of energy, according to the number of
times they have crossed over. There will, however, be a minimum
of energy lost corresponding to the case of a single traverse.
The sharply defined boundary of the oblique ray sheets can be
taken as the expression of this minimum. ‘The other boundary of
the rays is at this stage scarcely marked at all, owing to the
indefinite range of possible energy losses of the particles in their
preliminary movements. Probably, also, the spreading of the rays
is conditioned partly by the great range of intensity of field as
we cross the narrow Crookes’ dark space.
At lower pressures (e.g. Fig. 5, Pl. VII), the particles will lose
little energy in their surgings, and so when finally ejected they
form a confined sheet. The large dark spaces characteristic of
these lower pressures are associated with more uniform fields;
this also will be favourable to the production of confined sheets
of rays.
To test these views of the phenomena a few experiments were
made with the two kathodes at different potentials. This was
attained by having the lower plate connected as before to the coil
terminal, while the upper plate was connected to it through a
considerable electrolytic resistance. [The photographs obtained
are unfortunately slightly out of focus (except Figs. 1 and 3,
Pl. IX), but they are clear enough to show the points referred to.]
The series, Figs. 1 to 5, Pl. [X, shows various combinations of
potentials and pressures. In Fig. 1 the upper plate was quite
disconnected externally. In the other cases it was connected
through various amounts of resistance.
The first thing noticeable is the inequality of the two Crookes’
dark spaces, the upper one varying continuously with the potential
and apparently vanishing when the plate is disconnected. This
VOL. XV. PT. III. 16
232 Mr Orange, On certain phenomena of the kathode region.
seems to confirm the observations of Schuster* on the relation
between the thickness of the dark space and the strength of the
current.
As regards the sheets of rays, the appearances in these experi-
ments agree fairly well with the explanations advanced above.
In Fig. 1, Pl. IX, the kathode rays from the lower plate strike the
upper one violently. Some of the rays graze the edge of the
plate and produce the sharp, nearly vertical shadow which may be
noticed. The upper plate emits secondary kathode rays, which
are not sufficiently powerful to travel far towards the lower plate,
but are very soon thrown out sideways as three highly luminous,
but ill-defined sheets, corresponding to the three sides of the
triangle.
In Figs. 2 and 4, Pl. IX, the form of the lower ray sheet is clear
and it will be noticed that in these cases it is much further away
from the kathode than in any of the examples on Pls. VI and VIII.
This is probably due to the fact that rays from the upper (low
potential) plate will not have sufficient energy to approach near to
the lower kathode and hence when they finally start moving side-
ways they are at a considerable distance from it. No such feature
is associated with the upper plate. The rays starting from near
the latter form two distinct beams (two on each side that is)
in most of these examples. (e.g. Figs. 2 and 4, Pl. IX.)
These two beams might be explained as being due to
(i) the primary rays from the upper plate which have
travelled back after visiting the neighbourhood of the lower
one, and
(i) the secondary rays from the upper plate due to the
impact of the primary rays from the lower one.
The change which has occurred in the position and direction
of the “median” beams, owing to the alteration of the potential
of the upper plate, is quite what one would anticipate. (Fig. 2,
PX)
In conclusion, I wish to thank Prof. Sir J. J. Thomson for his
valuable suggestions and kindly interest in these investigations.
My gratitude is due also to Mr E. Everett for his ready
assistance at various times.
* Schuster, loc. cit. p. 556.
Phils Soe) Prock Xv., Pt 111. Pini IY,
Fig. 2
Fig. 1
PLATE VY.
Phil. Soc. Proc. xv., Pt 11.
I
.2 -
Ol
Or
Phil. Soc. Proc. xv., Pt tt. PLATE VI,
Fig. 2
mot?
Phil. Soc. Proc. xv., Pt m1. Puate VII.
ig. 4
Puate VIII.
ul. Soc. Proc. xv., Pt 11.
Ph
a
Phil. Soc. Proc. xv., Pt 11. PLATE IX.
Fig. 1 Fig. 2
Fig. 4
ERRATUM
P. 233, line 10 from top, for species read examples.
Mr Harding, Note on two new Leeches from Ceylon. 233.
Note on two new Leeches from Ceylon. By W. A. HaRpIne,
M.A., Peterhouse.
[Read 3 May 1909.]
The leeches here described were collected in Ceylon by Miss
Muriel Robertson, who very kindly sent them to me for examina-
tion, together with information respecting their habits and the
hosts upon which they were found.
The material placed at my disposal was not in a condition
very favourable for the examination of external features. It
comprised examples of two species hitherto unrecorded, of which
a brief description is given below.
1. Ozobranchus shipleyt, nov. sp.
Kleven species, fixed in corrosive sublimate and preserved in
alcohol, were examined. The largest specimen was 5 mm. in
length; this species therefore is one of the smallest of known
leeches.
Body depressed, divided into two distinct regions and generally
resembling Branchellion in form. Complete somite formed of
three rings. Abdominal region of the body provided with eleven
pairs of digitate branchiae, the posterior smaller and less branched
than the anterior pairs.
Anterior sucker not distinct from the body. Acetabulum
- cupuliform, shallow, centrally-attached and very large, its diameter
being equal to nearly one-third of the total length of the animal.
Hyes two (2).
Habitat :—Fresh-water; parasitic on the Ceylon terrapin,
Nicoria trijuga.
I have associated with this species the name of Mr A. E.
Shipley, to whom J am indebted for much kind help and advice.
2. Glossiphonia ceylanica, nov. sp.
The species is founded upon one specimen preserved in
alcohol. This had assumed a brown colour, somewhat lighter
upon the ventral surface. Irregular, black, median and marginal
patches and traces of four longitudinal brown stripes were seen on
the dorsal surface.
Head distinct from the much depressed and slender body.
Six eyes arranged in two sub-parallel rows, the first pair ap-
proximate.
16—2
234 Mr Harding, Note on two new Leeches from Ceylon.
Counting the first oculiferous ring as the first ring, the eyes
occur on the first, second and fourth rings; the male genital
opening lies between the 26th and 27th rings and the female
opening between the 29th and 30th rings (?); the anus lies
between the 68th and the 69th (and last) rmg; and rings 66, 67
and 68 are partly double.
Length, in alcohol, about 72 mm,
Habitat :—Ceylon, in fresh-water ; parasitic on the soft-tortoise,
Emyda vittata.
- Mr Sinclair, Note on abnormal pair of appendages, etc. 235
Note on the abnormal pair of appendages in Lithobius.
By F. G. Srvcuair, M.A., Trinity College.
[Received 3 June 1909.]
The presence of an abnormal extra pair of appendages is of
interest to me, as I have examined a great number of abnormalities
in the Myriapoda, but I am inclined to give a different inter-
pretation to the facts from that given in the note referred to by
Doneaster*, in which the appendage is taken to be a reduplication
of the poison claw.
The abnormalities which are very frequent in Myriapods fall,
in all cases that are familiar to me, into two classes. A re-
duplication in the transverse axis of the body or appendage, or a
reduplication in the longitudinal axis of the body or appendage.
The former is the more frequent—an example being a reduplication
of part of the antenna or leg forming a bifurcation.
The description of the small processes described as teeth,
jointed to the base of the appendage and the drawing of them,
remind me strongly of two small processes which are commonly
present on the end of the larval appendages in Myriapods. They
are moveable by muscular fibres, and, as the animal grows up, one
of them usually degenerates and disappears while the other changes
to a claw or spike.
“In the reduplication of a part in the longitudinal axis I should
think it more likely that the abnormal part would be posterior to
that of which it was a copy, following the order in which the
normal segments are formed.
It results from these considerations that I take the abnormal
appendage described in the note to be a reduplication, not of the
poison claw, but of the second maxilla. The basal joint with the two
small processes I believe to be an imperfectly formed transverse
reduplication of the other branch, so that if the development
had gone a step further there would have been two similar
branches on either side.
_ According to my view the undivided plate at the base would
be—not the coalesced basal joints of the poison claws, but a
metamorphosed sternal plate. .
Of course if a poison gland and duct had been found present
it would have upset this view, but that does not seem to have
been the case. It is worth remembering that in the Myriapoda
portions of proliferous tissue from which complete segments are
formed normally are present till comparatively late in life. The
complete number of segments in Diplopoda is not present for
a long period.
* Proc. Camb. Phil. Soc. xv. p. 178.
236 Mr Thomas, On a specimen of the cone
On a specimen of the cone Calamostachys binneyana (Carv.).
By H. Hamsuaw Tuomas, B.A., Downing College. [Communicated
by Mr E. A. Newell Arber.]
[Read 3 May 1909, ]
Forty years have now elapsed since the first description of the
cone Calamostachys binneyana was published*, but hitherto no
petrified specimen has been found showing its connection with
vegetative organs of any kind.
In December last, I received a specimen of a cone with four
whorls of Calamite leaves attached to the base, derived from the
Halifax Hard Bed at Huddersfield. The cone was at least 14 mm.
long and about 5 mm. broad. It was cylindrical in shape and
eight whorls of sporangiophores are preserved.
The structure of the cone agrees closely with that of specimens
previously described+, and the axis and sporangiophores do not
present any unusual features. Several of the bracts are very well
preserved and show some new points of interest. As usual, they
are coherent at the base to a disc, and, on becoming free, turn
sharply upwards. Each is provided with a vascular bundle, the
centre of which is occupied by a group of very small xylem
tracheides surrounded on all sides by small thin-walled cells,
probably phloem. The bundle may possibly therefore be con-
centric in structure and not collateral as formerly supposed, though
it is very difficult to arrive at any certain conclusion. The free
portion of the bract bears a striking resemblance to a leaf. It
consists largely of sclerenchymatous fibres on the adaxial side,
while a layer of rudimentary pallisade tissue forms the other side.
The small bundle occurs in the centre of the bract, and on the
inner side of the pallisade tissue, a zone of cells with dense black
contents is found. There is a thin epidermis on the outside.
At the base of the cone, there is a whorl of bracts resembling
the leaves still more closely. Immediately below this we havea
whorl of appendages differmg completely from the leaves, bracts,
and sporangiophores, and seen in longitudinal section as a broad
* Carruthers, W. ‘On the fruit spike of Calamites.” Jowrnal of Botany,
vol. v. 1867.
+ Binney, E. W. ‘‘ Observations on the Structure of Fossil Plants.’? Mem.
Pal@ontographical Soc. p. 24. 1868. Williamson, W. C. “On the organisation
of the Fossil Plants of the Coal measures,” Parts Iv. x. x1.xv. Phil. Trans. 1873,
1880, 1881, 1889. Hick, T. ‘‘On Calamostachys binneyana.” Proc. Yorks. Geol,
and Polyt. Soc. vol. x11. pt. tv. 1893. Williamson, W. C. and Scott, D. H.
‘Further Observations on the organisation,’ etc. Phil. Trans. 1894. ~
Calamostachys binneyana (Carr.). 237
ring of parenchymatous tissue. This may be compared with
the annulus of the cones of modern Equisetums. It contains
however some rudiments of vascular tissue. The discovery of
this organ further illustrates the similarity between the Paleozoic
Calamites and modern Equisetacez.
Below the “annulus” there are four whorls of foliage leaves.
These are small linear, rather falcate structures, about 5 mm.
long, less than 1 mm. broad, and free at the base. They are
almost identical in their size, form, and arrangement, with those
known from impressions as Calamocladus grandis (Sternberg).
The structure of the leaves differs somewhat from those which
have been already described*. The upper portion consists of
a large strand of sclerenchymatous fibres running the whole
length of the leaf but smaller than that occurring in the bracts.
A small bundle occupies the centre of the leaf, and below, there
is a band of cells with dense black contents. The latter is
crescentic in transverse section and separates the pallisade tissue
from the bundle and fibres; its function is not yet certain. The
pallisade tissue is greater in amount than in the bracts, and
consists of radially elongated cells with thin walls and numerous
intercellular spaces. On its outside, there is a narrow epidermis.
Stomata are seen in some places, and were probably slightly sunk
below the surface of the leaf.
The internodes of the stems between the leaf whorls seem to
have been covered with small hairs, which also occur on the
lower part of the cone. They are preserved as small, dense,
black bodies, and may perhaps have been glandular.
The form of the cone and leaves shows that it is probably
identical with the impressions named by Weiss + Paracalamostachys
williamsont, and also with Zeiller’s Calamostachys grandis}. It
seems possible that the name Calamostachys binneyana should be
applied as indicating a type of structure rather than a species, and
hence the name Calamostachys grandis is perhaps the best desig-
nation for the cone described here.
The discovery of this specimen is of interest for several
reasons. It furnishes for the first time direct evidence that this
well-known cone was borne on a Calamite plant. The question of
its affinities—at one time debated with keenness—was practically
settled some years ago, but the stem and leaves of the plant have
* Hick, T. ‘‘On the structure of the leaves of Calamites.” Mem. and Proc.
Manchester Lit. and Phil. Soc. vol. 1x. p. 179. 1895.
+ Weiss, C. KE. ‘‘Steinkohlen-Calamarien 1.” Abhandlungen zur geologischen
Specialkarte von Preussen, Band v. p. 193. 1884.
+ Zeiller, R. Flore fossile dw bassin houiller de Valenciennes, p. 376. Pl. 59,
Figs. 4—7. Paris, 1886.
238 Mr Thomas, On a specimen of the cone, ete.
hitherto remained unknown. The leaves have now been dis-
covered, and there is little doubt that, before long, a petrified
stem bearing leaves of this kind will be found. The “annulus”
and the hairs on the stem are here described for the first time.
The great similarity of structure between the foliage leaves
and the bracts of the cone is also a point of some interest, as
indicating the foliar nature of the latter. This, together with
the probable occurrence of an annulus in Calamostachys, is of
some importance in the discussion of the morphology of the cones
of the Equisetales.
My best thanks are due to Mr Arber for his kind advice and
assistance in this work.
Mr Gregory, Note on the Histology of the Giant, etc. 239
Note on the Histology of the Giant and Ordinary Forms of
Primula sinensis. By R. P. Grecory, M.A., St John’s College.
[Read 17 May 1909.]
(PuatE X.)
During the last few years the Giant form of Primula sinensis
has become well established in cultivation, and is now known in
many of the numerous horticultural varieties of this genus.
Nothing definite is known as to the origin of the form, nor can
we at present say anything as to the behaviour of the Giant and
Ordinary characters in cross-breeding, although experiments are
now in progress in this connexion.
Flowers of the two plants described. In each case the upper flower is newly
opened, the lower is older. Scale divided in inches. From a photograph.
Plants of the Giant form are of a somewhat coarser general
habit than those of the usual form. As compared with the latter,
they are characterized by the stoutness of their stems and petioles,
and by their larger leaves and flowers. In Giants of the “Stellata”
type, the petal-lobes are broad, and, unlike those of the ordinary
form, overlap one another to a greater or less degree (see text
figure). My experience of the seeds of the Giant form is limited
to those obtained this year from a few plants; they were, on the
average, larger than those of the ordinary type. I am indebted
240 Mr Gregory, Note on the Histology of the Giant
to Mr Leonard Sutton for further information on this point; he
writes: “With regard to the size of the seeds, we do not find
much difference in the Stellata forms, but in the Florist’s type,
seed of the Giant varieties, though variable from year to year, is
always larger and flatter than that of the smaller flowered sorts.”
At Professor Bateson’s suggestion I have made observations
with a view to comparing the nuclei of the two forms. The
plants chosen for the purpose were (1) a Giant White Star with
dark red stems, and (2) a White Star of the ordinary habit, but
closely resembling the Giant in all other characters. For both of
these plants I am indebted to Messrs Sutton of Reading.
The primary object of the investigation was to discover whether
there might be a difference in the number of the chromosomes in
the two forms, an idea suggested by the results of Miss Lutz* and
Gates} in Oenothera gigas. Upon this point the answer is definitely
in the negative; the number of the chromosomes is the same in
both forms of Primula sinensis, viz. 12 (reduced) and 24 (somatic).
The reduced number of chromosomes is shown with quite diagram-
matic clearness in sections transverse to the spindle at metaphase
or anaphase of either of the two meiotic divisions (figs. 1 and 2).
In the somatic divisions the chromosomes are more closely crowded
and their precise number is less easy of determination; but several
counts have given numbers ranging from 22 to 24, and there can
be no doubt, I think, that the number may be correctly stated at
24, I have no evidence which suggests that there is any tendency
to variation in the number of chromosomes which occur in the
somatic mitoses found in various regions of the floral organs.
But although the two forms are alike in the number and form
of the chromosomes, they give very distinctly the impression that
a difference exists between them in the size of the chromosomes
(at any rate as they appear at metaphase of the heterotype
division), in the size of the resting nuclei, and correspondingly in
the size of entire cells.
In testing this point the comparison between the two forms
was made by means of figures drawn to exactly the same scale
with the help of a camera lucida, and by measuring the resting
nuclei with an ocular micrometer, the measurements being taken
along, and at right angles to, the long axis of such nuclei as were
not circular in outline. The drawings and measurements were made
upon material which had been carefully fixed, and showed little or
no signs of shrinkage during the process. The material was cut
in paraffin into sections sufficiently thick to contain entire nuclei
which had been untouched by the knife of the microtome. Ina
* «A Preliminary Note on the Chromosomes of Oenothera Lamarckiana and
one of its Mutants, O. gigas.” Science, N. 8. 26, p. 151, 1907.
+ “The Chromosomes of Oenothera.” Ibid. N. 8. 27, p. 193, 1908.
and Ordinary Forms of Primula sinensis. 241
few test cases the vertical measure of the nucleus was estimated
by focussing on to the upper and lower walls of the nucleus by
means of the micrometer fine adjustment, taking the mean of
three readings. In each of these cases the measure so obtained
approximated very closely to those taken in the horizontal plane.
It is of course desirable that the tissues selected for com-
parison should be composed of cells which approach, as nearly as
may be, to uniformity of shape and size. Such tissues are to be
found in various epithelial layers, notably in the very regular
layer of cells which surrounds the embryo sac in the mature
unfertilized ovule. This layer is the “couche de revétement” of
Warming* and Vesquet, and the “tapetum” of Billings, all of
whom have recorded its existence in species of Primula. Other
layers whose nuclei have been compared are the epidermis of the
young stigma as seen in approximately median longitudinal section,
and the epithelia of the young developing ovules. Equally favour-
able for purposes of comparison are the nuclei of the pollen mother
cells, since the individual cells at the same stage of development
are remarkably uniform in size, and the stages are marked by
easily recognizable characters of the nucleus, so that a just com-
parison can be made. I hoped to test the matter further by
measurements of the cells of the young embryos as they developed
within the seed, but owing to the resistance offered by the thicken-
ing integuments to the penetration of the fixing fluids I was unable
to obtain sufficiently good material. The apex of the young
radicle may perhaps allow a further test, when it becomes available
later in the season.
In dealing with the size of the chromosomes of the two forms,
I have had to be content with a comparison of the drawings made
with a camera lucida, since the chromosomes are too small to be
measured with any degree of accuracy by means of an ocular
micrometer. Figs. 1 and 2 show the groups of chromosomes of
the Ordinary and Giant forms, respectively, as they appear at
metaphase of the heterotype division. The figures represent the
view transverse to the spindle; the outlines of the chromosomes
were carefully drawn, and I think the difference between the two
is not exaggerated. Spindles seen in longitudinal view show that
the two forms had reached as nearly as possible identical stages;
a similar slight difference in the size of the chromosomes of the
two forms is apparent also in these longitudinal views. In the
somatic mitoses which I have seen the chromosomes were too
crowded to permit of fair comparison.
* “DeVOvule.” Ann. des Sci. Nat., Ser. vi. Tome 5, p. 235, 1878.
+ ‘Sur le Développement du Sac embryonnaire.” Ibid., Ser. v1. Tome 8, p. 360,
1879.
t ‘“Beitrage z. Kenntniss d. Samenentwickelung.” Flora, 88, p. 277, 1901.
242 Mr Gregory, Note on the Histology of the Giant, ete.
I give in the table (p. 243) some measurements taken from
edge to edge of the group of chromosomes in the equatorial plane
of the heterotype division, but any difference in size thus indi-
cated is perhaps not very trustworthy, since it is slight and its
measurement depends entirely on reading by the eye to fractions
of the micrometer scale.
But in the nuclei of the pollen mother cells and in the resting
nuclei of the various epithelial layers the differences indicated by
a comparison of the camera drawings are clearly borne out by a
comparison of the measurements (see table), all of which show the
same result, namely, that the nuclei of the Giant plant are, on the
average, larger than those of ordinary form, in the proportion of
from 4 to 10°/, of each diameter. In the case of the developing
pollen mother cells great care was taken in choosing exactly com-
parable stages, though, as a matter of fact, there appears to be
only slight change in size when the cells have reached the stages
under consideration. Figs. 3 and 4 represent the stage whose
measures are recorded under the head “Prophase, with looped
thread”; figs. 5 and 6 represent those recorded under the head
“ Prophase, diakinesis.” The nuclei selected for measurement were
chosen at random, with the provision that any nuclei that showed
any signs of shrinkage or distortion during fixation, or were cut
by the knife, were excluded. In making the measurements the
divisions of the micrometer scale were read to fifths by the eye;
to this extent therefore the measurements are only approximate,
but the preponderance of the measurements obtained for the
Giant over those obtained for the ordinary form, in the average
of a number of measurements, although not great, is, I think, too
consistent and regular to be accounted for by experimental error.
Perhaps the clearest evidence is to be obtained from an
examination of the columnar cells of the ovule, to which reference
has already been made. Both in the measurements and in the
drawings these show a very consistent difference in size. Fig. 7
represents nuclei from this layer, the upper row being those of the
Giant, the lower row those of the ordinary form. It will be
noticed that the third and fifth are the largest nuclei in the
lower row; they are almost exactly equal in size to the first and
fourth of the upper row, which are, to say the least, distinctly not
the largest of that row. In the ordinary form some care was
exercised in the selection of the nuclei to be drawn, lest any
difference might be unintentionally exaggerated. The nuclei
shown in the figure were afterwards measured; the average of
the measures of the six nuclei of the ordinary form was found to be
3°7 x 3°4 scale divisions, while the average in the case of the six
nuclei of the Giant was 39 x3°7. If these figures are compared
with those given in the table, it will be seen that the difference is,
if anything, diminished rather than exaggerated in the figure.
Q[NAO }eYy UT
s1eyjo Aue ueyy 1esaey
YONU sv pu sIsozrUI
JO josuo 949 jo susis
poemoys ysesrey, oy, |
She CMe
Aq 4nd o.taM 10 Surpratp
e1eMm yeyg Aue Sury91UL0
‘peNsvoUl 910M STTIO OATS
-S9D0NS JO TojonuU OT, »
GE xX Ge
PE X 9-6
(04) 0. x 0-8
(0M4) Z-€ x FE
PX EP
(om) 0-G x F-G
Whiz Ohai7
Sie SOS}
SYIVUIOYT
(storstarg e[¥og)
qSo][BULg
(suorstatq e[B0g)
qsoolery
(‘xdqy)"! =$L-T x
0G
0G
"SAT, OTROG
eZIg osBI0Ay
syuyy 07 Ajoyeurxordde peer orem suorstarp yy, “A FL.1 =
poinsvaut
Teponu
JO °ON
Areulpagd ORS
: -okiqute pozijyazeyuN 91nqeut
, SuUIpUNo.Ins s{Teo reumnypoo
AreurpiQ| sepnao Sutdoyeaep Jo “jog
queLy) i ‘suvIy, UL ‘sT[eo yetpeygidd
AveutpiQ| ewsyg Sunox jo uoroog
quel) ‘suoTy ueIpey, ut ‘stuteprdq
Aveurpa
ae ‘SUBIY, soyeig | 2
Areutpio esvydejeyy |, >
eo FS “Suory z
°
=e (9-4 ig ‘eeg) ( =
quriy) sisouryerp ‘oseydorg| &
fe)
©
| APapdo| (F » @ ‘s8y) proawyy =
quetx)) pedoor yy1m ‘eseydoag
‘oko ayy Aq
Ajoyeutxoidde si uolstatp opeos yovs ‘aatoalqo oryetuorypoody
“WU Z SSIOZT © YAIM pos/) ‘LOJOWOIOT Te[nog sstezy ve fo SUOISTATP oy} jo sulto4 UL Po9pLODNT OOM SoINSBoOUl OU",
SSWUOL AUVNIGUQ ANV INVI4) FAL NI THIONN 40 SINANHYASVA] JO AIA,
244 Mr Gregory, Note on the Histology of the Giant
As a further test drawings were made of the six largest nuclei
to be found in this layer in one section passing through the ovule
in an approximately median plane. The result is shown in
fig. 8, in which the left hand row represents nuclei of the
ordinary form, the right hand row nuclei of the Giant. The
difference here is obvious. Lest chance should have favoured the
Giant, further drawings were made of the ordinary form, choosing
the largest nuclei which could be found in the serial sections of
some four or five ovules which were mounted on the same slide.
The six largest of these are reproduced in fig. 9; it will be noticed
that they are rather smaller than the six nuclei drawn from one
section of one ovule of the Giant form.
Evidence has been given above which I think clearly suggests
the existence of a difference in size between the nuclei of the
Giant and ordinary forms. It remains to compare the size of
entire cells. It is very desirable that in instituting this com-
parison measurements should be made of the living pollen mother
cells and living pollen grains, but at the time when material of
this kind was available the trend which this work has since taken
was unforeseen. Microtome sections of growing tissues are, at the
best, unfavourable for making measurements of entire cells, and in
default of measurements of isolated cells such as might be pro-
vided by the pollen, I have had recourse to hand sections of the
living tissues of the stems and petioles. ‘Transverse sections were
cut from the living material and mounted in water, so that no
disturbance due to shrinkage was possible. Care was taken to
avoid any disturbance due to the drag of the razor in cutting.
Measurements of the diameters taken when the sections were cut
show that the stems and petioles of the Giant are thicker than
those of the ordinary form, the proportional difference being about
4 to 12°/, of the diameters, or of the same order of difference as
that found in the size of the nuclei. The size of the individual
cells encountered in such sections is naturally very divergent, but
by drawing the outlines of the cells to exactly the same scale
the difference in their size in the two forms is strikingly shown.
A number of drawings were made in this way from sections of
various comparable regions of the stems and petioles. Two pairs
of these drawings are shown in figs. 10 and 11, and 12 and 13.
The figures represent sections, chosen at random from a number
floating in a watch glass, of the main flowering stems of the two
forms, in each case taken half way between the base of the stem
and the lowest umbel of flowers; figs. 10 and 11 show the region
of the pith, and figs. 12 and 13 the cortical region, in the ordinary
and Giant respectively. It will be noticed—what has been found
to be the case in all the sections made—that the cells of the Giant
and Ordinary Forms of Primula sinensis. 245
are, cell for cell, larger than those of the ordinary form, and that
to a degree sufficient in itself, I think, to account for the greater
thickness of the Giant. Just the same resemblance in structure
and difference in size is found in other regions of the stem and in
the petioles of the leaves; the difference is sufficiently illustrated
in the figures of the stem, and I have not thought it necessary to
multiply the number of figures in order to illustrate the petioles.
In these observations there is, I think, strong ground for the
suggestion that the difference between the Giant and ordinary
forms may be referred to a difference in the size of the cells;
that is, the character of Giantness manifests itself in the cells
themselves and not merely in the plant as a whole. At present
only a suggestion can be made, for we are as yet ignorant as to the
extent to which individual variations among plants of the same
type may affect these results; my observations have been limited,
for want of others, to one pair of plants. I hope in the future to
make a comparison between a number of Giant and ordinary
plants, grown, as were the pair described here, under similar
conditions.
EXPLANATION OF PLATE X.
The figures were all drawn with a Camera lucida. Figs. 1—6, 8,
and 9 were drawn with a Zeiss 2mm. Apochromatic Obj., 18 Ocular.
For fig. 7 the same objective with Ocular 8 was used. Figs. 10—13
were drawn with a in. objective.
Fig. 1. Ordinary form; metaphase of the heterotype division in
the pollen mother cell, the section being transverse to the spindle.
x about 3200. |
Fig. 2. Giant form; as fig. 1.
Fig. 3. Ordinary form ; prophase of the heterotype division of the
pollen mother cell. x 3200.
Fig. 4. Giant form ; as fig. 3.
Fig. 5. Ordinary form; later prophase (diakinesis) of the hetero-
type division, the chromosomes in the form of gemini. x 3200.
Fig. 6. Giant form; as fig. 5.
Fig. 7. Nuclei from the layer of cells surrounding the embryo sac ;
the upper row from the Giant, the lower row from the Ordinary form.
x 1420.
Fig. 8. Nuclei from the same layer; the left hand row from the
Ordinary form, the right hand row from the Giant form. The nuclei
shown were the largest to be found in one section of an ovule in each
case. x 3200.
246 Mr Gregory, Note on the Histology of the Giant, ete.
Fig. 9. Nuclei from the same layer. The nuclei shown were the
six largest to be found in the serial sections of four or five ovules of the
Ordinary form. x 3200.
Fig. 10, Pith cells and primary xylem from a T. 8. of the flowering-
stem of the Ordinary form. x 210.
Fig. 11. The same in the Giant form. x 210.
Fig. 12. Cortical cells from a T. 8. of the flowering-stem of the
Ordinary form. x 210.
Fig. 13. The same in the Giant form. x 210.
OG, SO", IP iii,
Phil. Soc. P1
C)
Co)
C
g
OQVOE ©
QOOOGOG ?
Mr Purvis, The influence of dilution on the colour, etc. 247
The influence of dilution on the colour and the absorption
spectra of various permanganates. By J. E. Purvis, M.A,
St John’s College.
fiead 17 May 1909.
y
[Puate XI.]
It has always been considered that permanganate solutions
show similar absorption bands whatever be the nature of the
element or group of elements acting as the positive ion. Ostwald’s
experiments * comparing the absorption spectra of the solutions
of a number of permanganates, whereby there appeared to be no
change either in the position or the width or the intensity of the
bands, appeared to prove conclusively that such absorptions were
independent of the nature of the positive ion. The only criticism
which could be brought against the experiments was, and is, that
sufficient dispersion of light had not been used. It is probable
that any changes would be exceedingly small, and in order to
distinguish small differences, if there are any, it would seem
to be desirable to use a greater dispersion than was used by
Ostwald.
It is also well known that dilute solutions of permanganates
gradually change their colours when they are kept for some time,
and it is usual to explain such changes by the action of light.
The change is only noticed in very dilute solutions, and, ordinarily,
a brown colour is produced. No observations are recorded with
regard to changes in the absorption bands during the colour
changes; nor are there any observations to indicate that the
changes take place in the dark, or out of contact with the air.
The following description gives some account of experiments
conducted in these directions.
Expervmental part.
The separate bands of solutions of permanganates can only be
seen when the solutions are very dilute: and, after some preliminary
trials, the following standard solutions of the permanganates of
barium, zinc and potassium were made:
0375 gram barium permanganate dissolved in 1000 c.c. distilled
water,
0°262 gram zinc permanganate dissolved in 1000 cc. distilled
water,
0316 gram potassium permanganate dissolved in 1000 ce.
distilled water.
Three separate solutions of each salt were investigated, and
* Zeits. physik. Chem. Vol. 1x. (1892), p. 579.
VOL. XV. PT. III. 17
248 Mr Purvis, The influence of dilution on the colour
each solution contained the same amount of permanganate. The
solutions were placed in their respective cells or troughs, one of
which was 5 mm. long, a second one was 154 mm. long, and a
third one was 310 mm. long. The comparative solutions were,
therefore, made by diluting ‘the strongest one 30°8 and 62 times
respectively.
The apparatus used in these experiments has been previously
described* by the author in some experiments on the absorption
spectra of solutions of various salts of didymium and erbium. The
source of light was a Welsbach burner without the glass, whose
rays passed “through a small circular aperture and thence carried
through the solutions by a quartz lens; and the emerging light
was focussed on the slit of the spectroscope. The times of exposure
varied from 1, 3 and 5 minutes; but the same length of time was
allowed for each series of comparative observations. In order
to make the comparison as strict as possible, blank tubes con-
taining distilled water and of exactly the same lengths and
diameters as those containing the solutions were placed in front
of the sht when photographs. were taken of the stronger solutions
contained in the 5 mm. cell. By this arrangement, the light rays
passed through the same thickness of water.
In the preliminary series of observations photographs were
taken immediately after the solutions were made; and although
there appeared to be no difference in the colour of the solutions,
there were differences in the width of the bands as well as in the
amount of general absorption of light in the more refrangible
parts of the spectrum. After the solutions had stood for some
hours changes in the colour of the dilute solutions were also
observed. Fresh solutions of the permanganates of barium and
potassium were then made, and they were allowed to stand two
days when photographs of the absorption spectra and changes in
the colour were noticed.
The following notes describe these observations; and in order
to shorten the description it should be stated that the phrases
“5 solution,” “154 solution,” and “310 solution” mean that there
was the same amount of permanganate in the tubes whose lengths
were 5 mm., 154 mm., and 310 mm. respectively.
The bands observed were AX 570, 546, 524, 504, 4864, and
they are numbered in the following notes so that
a 570 = 1,
546 = 2,
524 = 3,
504 = 4,
486 = 5.
* Proc. Camb. Phil. Soe. Vol. x11. pt. mm. p. 206.
+ Lecog de Boisbandran, Spectres lwmineux, p. 109.
and the absorption spectra of various permanganates. 249
The other bands were too faint to make any exact observations of
them.
i
Solutions of the permanganates of barium and potassium
were made and allowed to stand for two days in the full glare
of a well lighted room. They were then examined; and the
5 solutions showed the well known permanganate tint; whilst the
154 solutions were pink, and the 310 solutions were yellowish
brown.
A. Barium ermanganate :
F p 8 154 solutions.
Potassium do.
do. do. 5 solutions.
Band 1 was narrower in the 154 solutions than in the
5 solutions; band 2 was also narrower, and the differences were
well marked; band 3 was also narrower but the difference was
not so marked as in band 2, whilst bands 4 and 5 were a little
wider in the 154 solutions than in the 5 solutions. Also the
general absorption was much greater in the 154 solutions; and the
position of the bands in the 5 solutions was more towards the red
end of the spectrum than in the 154 solutions.
Barium —_ permanganate } 310 solutions.
Potassium do.
do. do. 5 solutions.
Bands 1, 2 and 3 were narrower in the 310 solutions, and
these differences were more marked than in the corresponding
bands of the 154 solutions; and the bands 4 and 5 were also much
wider than the corresponding bands of the 5 and 154 solutions.
Also the general absorption had greatly increased, and it was
greater in the 310 solutions than in the 154 solutions. The
position of the bands in the 5 solutions was also more towards
the red end of the spectrum: the difference in this respect was
more marked when compared with the 310 solutions than with the
154 solutions, .
B. The solutions were allowed to stand two days longer
and they were again examined, In the 154 solutions the general
phenomena were very like those observed before, except that
the general absorption had slightly increased. In the 310
solutions the general absorption had also slightly increased, and
the differences in the width of the bands 2 and 3 were much more
marked.
C. The solutions then stood for three weeks and they were
again examined. The 154 solution of barium permanganate was
a reddish brown colour; the bands 1, 2 and 3 were much narrower
than the corresponding bands in the 5 solution, and the bands
17—2
250 Mr Purvis, The influence of dilution on the colour
4 and 5 were wider than those in the 5 solution. The general
absorption was more marked in the 154 solution than in the
5 solution. The 154 solution of barium permanganate showed
that the bands 1, 2 and 3 had also become narrower, and the
bands 4 and 5 were wider; but the general absorption had not
altered much from the previous observation. The 310 solution
of barium permanganate was of a light brownish yellow colour
and perfectly clear. The 5 solution showed the five bands well
marked; and the 310 solution showed that the bands 1, 2 and 3
had almost disappeared, whilst the bands 4 and 5 had quite
disappeared and just beyond these there was complete general
absorption.
The colour of the 154 solution of potassium permanganate
was brown, and the solution was quite clear. The bands 1, 2 and
3 were much narrower than the corresponding bands in the
5 solution, whilst the bands 4 and 5 were a shade wider, and
just beyond band 5 there was complete general absorption;
whereas there was little or no difference in the colour or the
general absorption in the 5 solution. In the 310 solution of
potassium permanganate the bands 1, 2 and 3 were only just
visible ; bands 4 and 5 had completely disappeared, and there was
complete general absorption just beyond; whilst in the 5 solution
the bands were just as before, and there was no apparent change
in the general absorption.
The general results of the above observations indicate a
development of considerable differences in the more diluted
solutions both as regards colour and absorption bands. The
usual explanation is that light vibrations are the cause of such
changes. In order to test this, similar solutions of the perman-
ganates were made in the dark, and they stood covered up in
a dark cupboard so that no light could enter. The solutions were
examined after two days; and the following notes describe the
observations.
Il.
Solutions of permanganates of barium and potassium made in
the dark and allowed to stand for two days well covered up and
placed in a dark cupboard and then examined.
The colours of the 154 solutions had changed from the well
known permanganate tint to a pinkish colour; and the colours of
the 310 solutions had become a rose colour with a tinge of brown.
The strong 5 solution did not appear to have changed. The
absorption spectra of these solutions were also examined.
D. Barium permanganate } Ted aoleone:
Potassium do,
do. do. 5 solutions,
and the absorption spectra of various permanganates. 251
The change in colour was accompanied by some changes in
the appearance of the absorption bands. There appeared to be
little or no change in the band 1; band 2 was not so wide in the
dilute solutions; and similarly in band 3, although the difference
was not so well marked as in band 2; whilst in bands 4 and 5
there was little or no difference in the solutions. Besides
alterations in the bands, there was much more general absorption
in the 154 solutions.
EK. Barium ieee Ocala
Potassium do.
do. do. 5 solutions.
Band 1 in the 310 solutions was a shade narrower than the
corresponding band in the stronger solutions: the width of band 2
was much less in the 310 solutions (cf. the 154 solutions): band 3
had also decreased in width but the difference was not so marked
as in band 2; band 4 was also very slightly decreased in width:
whilst band 5 did not appear to have decreased, although there
was a slight difference in the intensity.
Also, there was much more general absorption in the 310
solutions. Besides these changes, the position of the bands 1
and 2, and in a less degree, band 3, 1s not so far towards the
red end as in the 5 solution, and the same remark applies to
bands 4 and 5 although the difference is not so marked.
The above solutions stood two days longer in the dark, and
they were again examined.
The colours of the 154 solutions were of a rose red tint—they
were not so brown as the solutions made two days earlier and
kept im the light; whilst the 310 solutions were yellow brown.
Potassium 154 solutions.
do. do. 5 solutions.
G. Barium a aaa
do.
There appeared to be little or no change in band 1 in all the
solutions; band 2 was much narrower in the 154 solutions;
band 3 in the 154 solutions was also narrower than in the
5 solution, but the difference was not so marked as in band 2;
bands 4 and 5 did not show a marked difference, although they
appeared to be a shade wider in the 154 solutions.
There was more general absorption in the 154 solutions, and it
had increased a little since the observations of two days ago.
H. Barium Benger SiG esln Mone
Potassium do.
do. do. 5 solutions.
Band 1 was not quite so wide in the 310 solutions as in the
252 Mr Purvis, The influence of dilution on the colour
5 solution; band 2 had decreased in width very considerably
in the 310 solutions; band 3 was also not so wide in the 310
solutions, but the difference was not so striking as in band 2;
and bands 4 and 5 have very slightly increased in width in the
310 solutions.
Besides these changes, there was more general absorption in
the 310 solutions, but the increase since the observations of two
days ago was not very great.
Also, the shift of the bands towards the red end as noticed in
E was similarly marked.
J. The solutions stood for three weeks longer in the dark and
they were again examined.
Barium _ permanganate } es ea
Potassium do.
do. do. 5 solutions.
The 154 barium permanganate solution was of a purplish
colour, and there was a slight opalescence; the 154 potassium per-
manganate solution was rose pink coloured and perfectly clear.
In the 154 barium permanganate solution the bands 1, 2 and
3 were again narrower than the corresponding bands in the
5 solution; whilst bands 4 and 5 were slightly wider, and general
absorption was more pronounced in the 154 solutions than in
the 5 solution. Similar remarks apply to the 154 potassium
permanganate solution.
K. Barium eta S10 colaone.
Potassium do.
do. do. 5 solutions.
These solutions were perfectly clear, and showed no opalescence.
The colours of the 310 solutions were brownish yellow.
The 5 barium permanganate solution showed the bands well
marked, and very little increase in the general absorption from
the earlier observations—the bands 1, 2 and 3 were very faint
and narrow in the 310 solutions, and just beyond this towards the
ultra violet there was complete general-absorption.
In the 310 potassium permanganate solution the bands 1,
2 and 3 were faint but they were better marked, and bands 4
and 5 were only just visible, but they were wider, than the
corresponding bands in the 5 solution. Just beyond band 5 on
the more refrangible side there was complete general absorption
in the 310 solutions.
So that these experiments prove that the changes of the
solutions made in the dark and kept from the influence of light
were very similar to those which had been subjected to the action
of light ; although light appeared to accelerate the rapidity of the
changes.
and the absorption spectra of various permanganates. 253
III.
In order to test the accelerative effect of light, solutions of
permanganate of zinc were made; one series in the light, and
allowed to stand in the full glare of the light of the laboratory,
and another series of solutions made in the dark and allowed to
stand well covered up with black cloth and placed in a cupboard
to which no light could penetrate. The solutions standing in the
light were examined by the eye from time to time. After six
hours a very slight change in the usual permanganate tint of the
310 solution was noticeable; but none in the 154 solution.
After 10 hours standing the 154 solution was still pink and the
310 solution was rose coloured. On standing 24 hours, the
310 solution was light yellow brown im colour, and the 154
solution was rose red. The solutions appeared to retain this
colour during another 24 hours.
After two days standing, the solutions which had been made
in the dark, and which had stood in the dark during this period
of time, were then examined and compared with those kept in the
light, and there appeared to be exactly the same changes in colour
in them.
L. Zine permanganate in dark .
ate ag iin lieth a 154 solutions.
do. do. in dark 5 solution.
Band 1 was not quite so wide in the 154 dark and light
solutions as in the 5 solution; band 2 was also narrower in the
154 solutions; band 3 was also narrower but not so well marked ;
whilst bands 4 and 5 appeared to be slightly wider in the 154
dark and light solutions. The general absorption in the solutions
kept in the dark and in the light was about the same in each,
and greater than that of the 5 solution, Also there was a
shght shift of the bands in the 5 solution towards the red
end more than in the 154 solutions, but the difference was not
well marked.
M. Zinc permanganate in dark } Si ccolahoree
do. do. in light
do. do. in dark 5 solution.
Band 1 was again not so wide in the dark and light 310
solutions as the corresponding one of the 5 solution; bands
2 and 3 were also much narrower in the dark and light solutions ;
whilst bands 4 and 5 appeared to be slightly wider in the dark and
light 310 solutions than in the dark 5 solution.
The general absorption of light in the solution kept in the
light was a shade more marked than that kept in the dark;
254 Mr Purvis, The influence of dilution on the colour
and both general absorptions were greater here than those in the .
154 solutions.
The shift towards the red end of the bands of the 5 solutions
was much better marked when compared with those of the
310 solutions than those of the 154 solutions.
The solutions were allowed to stand as before in the dark and
the light for two days longer and they were again examined.
N. Zinc permanganate in dark
ae: ne a tight f 154 solutions.
do. do. in dark 5 solution.
There was a very doubtful increase in the general absorption
of the 154 solutions as compared with the previous observations in
L, otherwise the differences in the appearances of the bands were
very like those in the previous observations. There was no
difference in the width and appearances of the bands of the
solutions kept either in the light or dark; the bands 2 and 3 were
narrower in these solutions than in the 5 solution, whilst the
bands 4 and 5 were very slightly wider.
QO. Zinc permanganate in dark ;
do. do. in light f 310 solutions.
do. do. in dark 5 solution.
There appeared to be but a very slight increase in the general
absorption of the 310 solutions as compared with the previous
observations; the bands 1, 2 and 8 were narrower than the
corresponding bands in the 5 solution, the band 2 being the most
marked in this respect, whilst bands 4 and 5 were slightly wider
than the corresponding bands in the 5 solution.
The shift of the bands towards the red end im the 5 solution
was distinct as compared with their positious in the 310 solutions.
The observations indicate that similar changes take place in the
zinc permanganate solutions as in those of barium and potassium ;
and that light accelerates the changes.
General conclusions.
The results prove that, during the time of the observations,
(1) in the stronger 5 solutions there did not appear to be any
marked change in the ordinary colour nor in the absorption bands
of the permanganates; (2) in the 154 solutions there were con-
siderable changes in the colour which slowly turned to a rose red
or reddish brown one accompanied by changes in the width of the
absorption bands 1, 2,3, 4 and 5 and an increase in the general
absorption; (3) in the 310 solutions the changes in the colour
were more marked and a brownish yellow colour was developed
and the absorption spectra of various permanganates. 255
with an almost complete obliteration of the absorption bands and
a greatly increased general absorption ; (4) a shift of the bands
of the 5 solutions to the red end of the spectrum as compared
with their positions in the 154 and 310 solutions, and this
shift appeared to decrease with increased refrangibility of the
absorbed rays.
In order to explain the different positions of the bands of the
different solutions, the observations of H. Becquerel* show that
such differences depend upon the concentration—the greater the
concentration, the greater the shift of the bands towards the red
end of the spectrum.
With regard to the other changes, attention is again called to
the observations that the changes take place whether the solutions
are subjected to the action of light or whether they are kept in the
dark, although light accelerates the changes. One explanation
is that the dissolved gases, the atmospheric gases, particularly
carbon dioxide, may have been the influencing causes. Against
this view is the fact tbat carbon dioxide usually converts man-
ganates to permanganates very rapidly; and oxygen would scarcely
act as a reducing influence, whilst nitrogen is completely inert.
Nor could the changes have been caused by any dissolved organic
substances, for the solutions were made in distilled water, and
from pure crystallised salts; and also, all the glass vessels were
well washed before use with a warm mixture of hydrochloric and
nitric acids. Nor could any organic substances have entered the
solutions, for the latter were always kept well covered up. Never-
theless, in order to eliminate the action of any extraneous gases or
dirt, another series of solutions of potassium permanganate was
made, and the glass bottles were filled to overflowing. The contents
were isolated from the air by well ground stoppers. The bottles
of one series were filled in the dark, and they stood in cupboards
to which no light could penetrate. A similar series of bottles
stood in a well lighted room and they were exposed to the full
action of light. The changes in the colour of the solutions were
exactly the same as in the earlier observations; but those of the
solutions exposed to the action of light were much quicker. Besides
the colour changes, a small bubble of gas collected in the bottles.
The absorption spectra were not observed.
The explanation which seems to account for the changes
is that the dissociating force of the water slowly acted upon the
+
dissolved permanganates, so that the ionic condition of R and
- +
MnO,, where R represents the metallic ion, broke down. One
may imagine that the MnO, ion undergoes further dissociation
* Compt. Rend. Vol. cit. p. 106.
256 Mr Purvis, The influence of dilution on the colour, ete.
into MnO, and O, or into MnO, and O,. In such dilute solutions -
the tension between the molecules of water surrounding the ions
must have been very considerable, and it may have been so great
as to destroy the MnO, condition, so that further changes took
place which became visible in changes of colour, in changes in the
width of the bands and in the liberation of oxygen; and these
changes would be accelerated by the vibrations of light. The
intermediate stages of the changes might be represented by the
narrowing of the bands 1, 2 and 3 and the widening of the
bands 4 and 5, and these might correspond to changes of the
MnO, ions into MnO, and O ions. The complete change in colour
from the well known permanganate tint to a light brownish yellow
colour in the more diluted solutions, the disappearance of the
absorption bands, aud the increased general absorption represented
the complete change into MnO, and O,. The MnO, would be
dissolved in the colloidal condition, and it would be represented by
the complete disappearance of the bands, and the increased general
absorption, whilst the oxygen partly escaped.
DESCRIPTION OF PLATE XI.
It has not been possible to reproduce all the original photographs comparable
with them in clearness and precision. The reproductions on the plate are from
photographs of original negatives enlarged one and a half times. The shaded parts
represent light issuing through the solutions; the light bands represent the absorp-
tion bands; and the lighter parts in the more refrangible regions represent general
absorption.
1. Barium permanganate, 154 solution.
2. do. do. 5 solution.
These solutions were made in the dark, and they were kept out of contact with
the light during the experiments. They correspond to paragraph G in the notes.
3. Barium permanganate, 154 solution.
4. do. do. 5 solution.
These solutions remained fully exposed to the action of sunlight. They corre-
spond to paragraph B in the notes.
It will be noticed that the weak band at \570 is almost obliterated, although it
can be easily seen in the original photographs and in the enlargements therefrom.
The narrowing of the bands at \\ 546, 524 and the widening of those at A\ 504, 486
in the diluted solutions when compared with those in the stronger solutions are
well marked.
5. Zine permanganate, 5 solution made in the dark and kept in the dark.
6. do. do. 154 do. 0. do.
Ue CO, do. 154 do. fully exposed to the action of light.
These solutions correspond to paragraph L in the notes.
8. Zine permanganate, 5 solution made in the dark and kept in the dark.
9. do. do. 310 do. do. do.
10. do. do. 310 do. fully exposed to the action of light.
These solutions correspond to paragraph M in the notes.
The band at \ 570 is only just visible; but the narrowing of the bands at
dA 546, 524 and the widening of those at \\ 504, 486 when compared with those in
the stronger solutions are easily distinguishable. The general absorptions of the
solutions 6 and 7 do not show very marked differences: but there is a little
difference in those of the solutions 9 and 10.
PLATE XI.
Phil. Soc. Proc. xv., Pt 110.
CY
9gv —
Oo —
V&G —
Qi ——
olsg —
me
ad)
7%
9gr —
vos —
VAS ==
ore) —
ols — |
Dr Barkla, Phenomena of X-Ray Transmission. 257
Phenomena of X-Ray Transmission. (Preliminary Paper.) By
Cuarues G. Barks, M.A., D.Sc. (Communicated by Professor
Sir J. J. THomson.) *
[Read 17 May 1909.]
The principal phenomena accompanying the transmission of
X-rays through matter may be classified under three heads—
Absorption, lonization, and Secondary Radiation.
Much that has been written on these subjects has been in the
form of disconnected papers, in which little attempt has been made
to collect and classify known experimental facts, or to give an
explanation of observed phenomena in terms of laws previously
discovered. As a consequence X-ray phenomena have been made
to appear much more complicated than they actually are.
In the following paper it is mtended to give, as briefly as
possible and without entering into experimental details, a state-
ment of facts already published, an account of the results of
further experiments, and a survey of the whole subject of X-ray
‘transmission, showing the connection between the various phe-
nomena and accounting for apparent anomalies. As the phenomena
of secondary radiation form the basis of classification they will be
discussed first.
Secondary X-Radiation.
Secondary X-rays of two distinct types have been found to be
emitted by substances subject to X-rays. Of these the scattered
X-radiation—one of the same penetrating power as the primary—
has invariably been found to be emitted during the transmission
of a primary beam through matter.
All the experiments that have been made on this radiation
have strikingly verified the theory of scattering, as given by
Sir J. J. Thomson+, many of the results being foretold as an
immediate consequence of this theory.
The second type of secondary X-radiation emitted by many
elements, and probably by all, is a homogeneous radiation
characteristic simply of the element. emitting it. Unlike the
scattered radiation this is distributed uniformly in all directions,
and gives no evidence of polarization in a primary beam where
such polarization exists. This radiation was shown by Barkla and
* The expenses of these researches were partially covered by a Government
Grant through the Royal Society.
+ Conduction of Electricity through Gases.
258 Dr Barkla, Phenomena of X-Ray Transmission.
Sadler* to be emitted only when the exciting primary radiation
was of more penetrating type. Also it was shown that beyond a
certain penetrating power of the primary, the intensity of this
secondary radiation from a given mass of substance was pro-
portional to the ionization produced by this primary beam in
a thin film of air. As we have no exact method of comparing the
intensities of beams differing in penetrating power, we are unable
to determine accurately the relative amounts of ener ey of different
beams reappearing as secondary radiation of this type. If, however,
We assume as approximately true that the ionizations produced in
a thin film of air by beams of equal intensity are proportional to
the absorptions of these beams in air, we may also say that the in-
tensity of this secondary radiation, bey ond a certain penetrating
power of the primary radiation, is proportional to the coefficient
of absorption of the primary radiation in aluminium. The relation
between the intensity of secondary homogeneous radiation and the
absorbability of the primary radiation may thus be approximately
represented by curve II in fig. 4 Whatever the accuracy of the
assumption, the general features of the curve remain unquestion-
able, i.e. first, no ~ appreciable intensity until the primary is more
penetrating; secondly, a rapid rise of intensity as the primary
is made more penetrating; and thirdly, a decline of intensity, ap-
proximately, if not accurately proportional to the absorbability
of the primary radiation. Mr Sadler? has recently investigated
the curves in detail on the same assumption, using a series of
homogeneous beams as_ primary radiations, and hes found the
same type of relation in all cases investigated.
The secondary radiation from a large number of elements has
been studied, and the percentage absorption of the radiation by a
sheet of aluminium ‘01 cm. thick, as measured by the diminution
of ionization in an electroscope 7 or 8 cms. from the radiating
elements, has been published by the writer.
When subject to a beam of X-rays of only moderate penetrating
power, the radiation reaching the electroscope from elements of
atomic weight between those of hydrogen and sulphur was almost
entirely a scattered radiation, none of the homogeneous type
appearing. Later analysis of the radiations from other elements
by Barkla and Sadler showed that the radiations from the elements
from Cr to Ag were practically homogeneous radiations, producing
in general, ionizations several hundred times the ionization pro-
duced by the scattered radiation from the equal masses of the
light elements. A weak scattered radiation was mixed with these.
* «Homogeneous Secondary Réntgen Radiations,” Phil. Mag., Oct. 1908,
pp- 950—584,
+ ‘* Transformations of Réntgen Rays,” Phil. Soc. Lond., April 23, 1909.
t ‘Secondary Réntgen Radiations,”’ Phil. Mag., June 1906.
Dr Barkla, Phenomena of X-Ray Transmission. 259
The writer has recently investigated more closely the radia-
tions from Sn, Sb, I (which have been recorded as elements
emitting a radiation of variable penetrating power). It has been
found that these consist of a very easy absorbed radiation and a
very penetrating homogeneous radiation superposed. The absorp-
tions of the penetrating portions of the beams from each element
are shown in fig. 1 on curve B. The percentage absorptions of the
soft radiations from these elements have not yet been determined,
but they are roughly indicated on curve A in fig.1. Though a
full analysis of the radiations from W, Pt, Au, Pb, Bi, etc. has
not yet been made, there is strong evidence that the observed
radiations from these elements are also principally homogeneous
radiations characteristic of the elements emitting them.
Percentage Absorption by Alf-o1 c.m.)
Atomic Weight of Radiator
Fig. 1.
Norz: ———— Continuous lines connect points which have been accurately
determined.
— — — Discontinuous lines pass through approximate positions of points.
As isianihe ts Dotted lines are hypothetical.
A knowledge of these characteristic radiations is sufficient to
account for the variations in the intensity and in the character of
the secondary rays emitted by different substances, and for what
have been regarded as anomalies in secondary radiation phenomena
by a number of investigators. Thus the intense radiation from
ethyl bromide when subject to a beam of ordinary penetrating
power is that given by the element bromine—an element in the
group of substances which emit homogenéous rays in considerable
intensity when subject to an ordinary primary radiation. The
variable behaviour of tin bichloride and of methyl iodide may also
be explained in terms of the results for tin and iodine already
published. The variations are due to the fact that a beam of
X-rays of ordinary penetrating power contains only a_ small
260 Dr Barkla, Phenomena of X-Ray Transmission.
proportion of rays of penetrating power higher than that of the
penetrating rays from Sn, Sb, and I; so that only a small pro-
portion of the more penetrating radiation is emitted with the
softer characteristic radiation. As the heterogeneous primary
radiation is made more penetrating a greater proportion of the
beam excites the penetrating secondary radiation. Thus the
intensity of secondary radiation and the average penetrating
power of this radiation increase rapidly.
By an examination of the curves connecting the absorption of
the various characteristic radiations with the atomic weight of the
radiating substance as shown in fig. 1 we are led to several
important conclusions. These characteristic secondary radiations
may be divided into several groups, the radiation belonging to
each group becoming more penetrating with an increase in the
atomic weight of the radiating substance. ‘Thus in fig. 1 we show
groups A and B.
If elements of low atomic weight emit characteristic secondary
radiations belonging to groups A and B, these radiations must be
exceedingly soft, and as a consequence must emerge from only a
very thin surface layer of the radiating substance. Owing to this
fact and to the absorption of the radiation in air before reaching the
electroscope, the effects of these radiations must be very small.
Such a soft radiation has been found to be emitted by Ca mixed
with the scattered radiation, and there have been indications of
such radiations from S and from Al. These, however, have not yet
been examined carefully.
As the atomic weight of the element increases, the character-
istic radiations become more penetrating and produce much
bigger ionizations in the detecting electroscope, almost completely
swamping the effect of the scattered radiation. As the atomic
weight of the element becomes higher still, the characteristic
radiation becomes so penetrating that only the most penetrating
constituent in an ordinary primary beam is able to excite it. The
intensity of the secondary thus diminishes, and finally the radiation
becomes inappreciable. But before this has happened the radia-
tion belonging to another group has appeared in appreciable
intensity, and this ultimately becomes the most important
secondary radiation. It appears very probable that there are other
groups similar to these, for even when the primary radiation is too
“soft” to excite the radiations A and B it is absorbed and it
produces ionization. And these secondary radiation phenomena,
as we shall see later, are connected with the phenomena of ab-
sorption and ionization. The hypothetical groups of radiations
softer than those in group A we shall denote by the letter X.
Dr Barkla, Phenomena of X-Ray Transmission. 261
Absorption.
Experiments on absorption of X-rays have been made by a
number of experimenters, but owing to lack of knowledge of
secondary X-rays, and to heterogeneity in the beams experimented
upon, little regularity of behaviour could be observed from the
experimental results.
= Lr
= a = N
Cu
@
Cr
7
SP,
SSEENG
SINCE
ellie FE
Ee
ie
=
Po
.
ee
FENN
eae
aa
a
NS
EEE gees
ee
wie
code
AS
EN
8 £ & 8
ee ere
ee
ae
Fa
:
ia
6
\
BS
ORCS SEES
Cis aes
eee ie
AEs Ealedra
A.
FE
Zr
ee
Fe-
We 2 49 ZOO MENS OMI OMMNIZO NENTS
0 140
i ABSORPT/ Al (4)
Fig. 2.
The connection between the absorption of X-rays and the
secondary radiation emitted from the absorbing substance was
first shown by Barkla and Sadler in a paper on “ Homogeneous
Secondary Roéntgen Radiations.” The laws governing the absorption
of X-rays have recently been more fully investigated*. The
* «The Absorption of Rontgen Rays,” Phil. Mag., May 1909.
262 Dr Barkla, Phenomena of X-Ray Transmission.
principal features brought to light by the investigation are
exhibited in curve IV in fig. 4, in which the absorptions by a
given element are plotted as ordinates, and the absorptions by Al
as abscissae.
In all the absorbing substances examined—C, Mg, Fe, Cu, Zn,
Ag, Sn, Pt, Au—there is approaimate proportionality between the
coefficients of absorption in a substance R say and in Al through
a wide range of penetratimg power. This approximate pro-
portionality holds until the primary radiation is made more
penetrating than the homogeneous radiation characteristic of
the absorbing substance R. Then the absorption begins to
increase more and more rapidly until, after reaching a maximum,
it begins to approximate again to proportionality with the absorp-
tion in Al, the ratio of absorption coefficients being now much
higher than before. The increase in the absorption was thus
shown to commence at the same point as that at which the
secondary homogeneous radiation began to be emitted, the con-
nection between absorption and intensity of secondary radiation
being shown by the curves IV and II. As the range of penetrating
powers experimented upon was that from the radiation characteristic
of Cr CG in Al= 136) to that characteristic of Ag (* in Al= 25),
it will be seen by comparison with fig. 2* that all elements,
one of whose characteristic radiations is between these limits,
showed the same feature in the absorption curve. All those
which did not emit a characteristic radiation of penetrating power
between these limits gave absorption curves without any special
deviation from the approximate proportionality. It is important,
however, to notice several features of the curves. The shape of
the curve for primary radiations is considerably more penetrating
than that necessary to produce the characteristic secondary radia-
tion in any substance approximated to the shape just previous to
the sudden rise in the absorption, showing the possibility of a
similar rise in the absorption having occurred with a much softer
radiation.
Again—and this is a most important point—the mass absorption
coefficients for a given radiation are in the order of atomic weight
of the absorbing substance when the corresponding radiations are
excited,
Thus using the very soft radiation from Cr, » in C, Mg and Al
are in order of atomic weight, but there is a step back for the
elements Fe, Ni, Cu, Zn, Ag, Sn because in these the radiation of
group B is not excited, and there is a further step back for Pt and
* Reproduced from paper on “The Absorption of Réntgen Rays,” Barkla and
Sadler,
Dr Barkla, Phenomena of X-Ray Transmission. 263
Au because in these the radiation A is not excited. When,
however, the primary radiation is sufficiently penetrating to
excite the radiation B in Fe, Ni, Cu, Zn, these take their proper
place. A radiation sufficiently penetrating to excite radiation
B in Ag, Sn, Pt, Au was not used, but when the radiation was
~
S
S
bn ae ee ee
--
\
QO
jm)
XN
Absorption | "1
Rather ‘soft’ Radiation
-— ee eee
S 50 100 150 200
Atomic Weight of Absorbing Substance
Fig. 3.
Nore; Letters X, A and B denote the characteristic secondary radiations
excited (see fig. 1).
sufficiently penetrating to excite the radiation A in Pt and Au,
these took their proper places with respect to Ag and Sn. :
Thus in fig. 3, curves J, II and III exhibit the relation
between the absorption in different elements and the atomic
weight of the absorbing element for three different radiations.
Curve I was obtained by using the very soft homogeneous radiation
VOL. XV. PT. III. 18
264 Dr Barkla, Phenomena of X-Ray Transmission.
from Cr . in Al= 136) ; Curve I by the fairly soft homogeneous
hack ee :
radiation from As i. in Al = 225) ; Curve III by the fairly pene-
p
5).
: Saks. PEER A.
trating radiation from Ag (- in Al = 2°
We thus see from these results that the absorption of a
homogeneous radiation by elements of various atomic weights is a
periodic function, but in general an increasing function of the
atomic weight. Though observations have not been made on a
sufficient number of elements to obtain the accurate relation
between absorption and atomic weight of the absorbing substance
for any one particular homogeneous beam, different portions of
similar curves have been obtained from observation of the absorp-
tion of other homogeneous beams, and their shapes reproduced in
the discontinuous curves in the figure.
Tonization.
An examination of the results obtained by ditferent experi-
menters on the ionizations produced in gases by X-rays showed
that these phenomena were in all probability also connected with
secondary X-ray phenomena, and that the numerous apparent
irregularities might be explained in terms of laws similar to those
found for absorption. The writer was therefore led to attempt an
investigation of the ionizations produced in different gases by
homogeneous beams varying considerably in penetrating power.
The radiations used were the homogeneous radiations from Fe, Cu,
Zn, Br, Sr, Ag, Sn, Sb, varying in absorbability as shown by curve
B in fig. 1.
The gases and vapours experimented upon were Air, O, COQ,,
SO,, C,H;Br, SnCl,, CHI.
The results of preliminary experiments may be briefly stated
as follows:
Range of penetrating power
Gas of radiation
O Fe radiation to Ag radiation
CO, 2° 2° 22
SO, 33 2” 23
C,H,Br Fe radiation to Br radiation
Br radiation to Sn radiation
SnCl, Fe radiation to Sn radiation
I radiation ...
CH,I Fe radiation to Ag aptte Sin
Results
Ionization approximately proportional to
ionization in air
2 2 2 29
22 2 Phy 29
BB) ? ” bb
Relative ionization increased approximately
tenfold
Jonization approximately proportional to
ionization in air
Relative ionization considerably greater
Ionization approximately proportional to
ionization in air [only slight gradual
change, if any]
Dr Barkla, Phenomena of X-Ray Transmission. 265
These results must be connected with the results of experi-
ments on secondary radiation and absorption. Carbon, Nitrogen,
Oxygen and Sulphur, elements in the group in which an appreciable
homogeneous radiation within this range of penetrating power
has not been detected, and in which there is proportionality of
absorption within this range of penetrating power, here exhibit
proportionality of ionization also.
Ethyl! bromide and Tin bichloride exhibit a like proportionality
in ionization until the radiation becomes more penetrating than
the radiations characteristic of Br and Sn respectively. For more
penetrating radiations the relative ionization increased just as the
secondary radiation in Br and Sn began to be excited and as the
absorption began to increase.
Absorption of Sec Radn.in Al ,
Intensity of Sec. Radn..
lonization
Absorption
Absorption of Primary in AL.
Fig. 4.
Methyl Iodide, which was not subjected to a radiation of more
penetrating type than that characteristic of Iodine, also exhibited
approximately the same proportionality of ionization.
We are thus led to the conclusion that as in the case of the
secondary radiation and absorption, the turning point in the
curves showing the relation between ionization and the pene-
trating power of the primary radiation is just where the primary
radiation becomes more penetrating than the homogeneous
radiation characteristic of the substance traversed, or of one of the
elementary constituents of the substance traversed.
18—2
266 Dr Barkla, Phenomena. of X-Ray Transmission.
General Discussion.
The various phenomena may therefore be connected as shown
in the diagram fig. 4
Line I represents the absorbability of the secondary radiation
characteristic of an element R say.
Curve II shows approximately the relation between intensity
of secondary radiation from R, and absorbability of the primary
radiation (measured in Al).
* Curve III shows the relation between ionization in R and
absorbability of the primary radiation (measured in Al).
Curve IV shows the relation between absorption in R and
absorbability of the primary radiation (measured in Al).
Curves II and III are based on the assumption that the
ionization in air is proportional to the absorption in air for beams
differing in penetrating power. The important features are beyond
doubt; the exact shape, however, depends on the accuracy of this
assumption.
There is thus an intimate connection between the absorption
of a primary radiation in a substance, the ionization in the
absorbing substance (when in the gaseous state), and the intensity
of secondary radiation from the absorbing substance. These are
periodic functions of the penetrating power of the primary radiation,
the three rising and falling together. Though two complete
periods have not yet been obtained in any one substance, there is
very strong evidence from the behaviour of different substances
that there are at least several maxima and minima to be obtained
by using a primary radiation of sufficient range in penetrating
power. “The periodicity in intensity of secondary radiation is not
one of intensity alone, for each fresh period brings a characteristic
radiation of different penetrating power.
Sufficient experiments have not yet been made in order to
determine if the periodicity is a true periodicity in the behaviour
of one system in the atom, or is due to different systems behaving
in a similar manner when subject to primary radiations of different
penetrating powers. Be that as it may, the experiments on
secondary radiation show that there are various characteristic
radiations; the experiments on ionization show that there are
various ionizations, only a part of the total ionization being con-
nected with one radiation; the experiments on absorption show
that there are various processes of absorption, only a part of the
total absorption being connected with one radiation.
It should perhaps be pointed out that it is owing to the fact
that absorption, ionization and secondary radiation connected with
one substance are periodic functions of the absorbability of the
primary radiation, that these three quantities are also periodic
Dr Barkla, Phenomena of X-Ray Transmission. 267
functions of the atomic weight of the substance subjected to a
fixed primary beam.
Many experiments remain to be performed before any theory
regarding the exact processes taking place during the transmission
of X-rays through matter can be established. It is, however,
worth while pointing out that if an electromagnetic pulse in which
the electric force is uniform from front to back of the pulse passed
over a number of independent electrons with a definite period of
vibration, the absorption would be a periodic function of the thick-
ness of the primary pulse. The absorption coefficient might be
written
PP
ee £ [1 cos 205 | ;
mm a )
where d is the thickness of primary pulse and 6 the wave-length of
the radiation emitted by the freely vibrating electrons, NV the
number of electrons in unit volume, e and m the charge and mass
of an electron. This would give an absorption curve of somewhat
the same form as those shown, and would also show periodicity.
As we have no method of measuring the thickness of the pulse,
and do not know anything of the force distribution in the pulse, we
cannot strictly compare the experimental curve with this.
It should also be pointed out that with a primary pulse
in which the force gradually increases from zero to a maximum
and gradually again to zero, the periodicity and indeed the
absorption of thicker pulses would practically disappear. In such
a case the periodicity would have to be explained by assuming
the existence of different absorbing, radiating and ionizable systems
in the same atom.
The connection between absorption, ionization and intensity of
secondary radiation might be easily accounted for. It would only
be after such an absorption of energy that electrons would be
hurled out of an atom, and ionization be produced—(both as a
primary and secondary or subsequent effect of this ejection). The
disturbance in the atom would set up an electromagnetic pulse
characteristic of the atom.
It seems very improbable for several reasons that the sub-
sequent bombardment of other atoms by the ejected electrons
produces an appreciable secondary X-radiation. The speed of
ejection has been found to depend on the penetrating power of
the primary radiation causing that ejection; so also would the
character of the secondary X-radiation produced by these. This is
contrary to experimental fact. Again, the connection between
the penetrating power of the primary radiation necessary to
produce a certain secondary radiation and the penetrating
power of that radiation would be very difficult to explain.
268 Dr Barkla, Phenomena of X-Ray Transmission.
Lastly, preliminary experiments on the secondary radiation from
alloys appears to indicate that the bombardment of a second
substance by the ejected electrons produces no change in the
character of the secondary radiation produced. The most difficult
point to explain is the fact that the primary radiation must be
just more penetrating than the homogeneous secondary radiation
characteristic of the exposed substance for that radiation to be
excited. This law appears to be an extension of Stokes’ Law of
Fluorescence to which the phenomenon of the secondary character-
istic radiation is akin.
The exactness with which the law is obeyed, and the striking
similarity between the various absorption curves indicates a de-
finiteness in the structure of the pulses, and the absence of
anything corresponding to variation in pulse structure.
As absorption of energy must precede the expulsion of electrons,
we might expect to find the intensity of corpuscular radiation
connected with the absorbability of the primary radiation in the
same way as is the X-radiation, except that the velocity would
vary with the penetrating power of the primary beam, as has
been found by Innes.
A detailed account of these experiments and a fuller discussion
will be published later.
LIVERPOOL.
Mr Kaye, The Emission of Réntgen Rays, ete. 269
The Emission of Rontgen Rays from Thin Metallic Sheets.
By G. W. C. Kaye, B.A., D.Sc., Trinity College, Cambridge.
(Communicated by Prof. Sir J. J. Thomson.)
[Received 4 August 1909.]
Pror. BracG and Dr MapsrEn* have, from the point of view
of the neutral-pair theory of the Roéntgen and y rays, made
measurements of the secondary corpuscular radiation which goes
forward and backward when y rays are incident on thin metal
sheets. They find in most cases a large want of symmetry in the
distribution of these secondary rays—there is more “emergence”
than “incidence” radiation: especially is this so for metals of low
atomic weight. For example, the ratio (f) of the emergence
intensity to the incidence is, in the case of soft y rays, about 13
for carbon, 7 for aluminium, 2 for the metals of the copper group,
1-1 for tin and lead: with hard y rays these numbers become
20, 7, 3 and 1 respectively.
MaDSEN+ obtained similar results in his investigation of the
distribution of the secondary y radiation produced by y rays under
analogous conditions. For zinc R (defined as before) is about 5,
for lead 7. He showed also that the y rays in passing through
matter are softened as well as scattered. The distribution of the
scattered radiation depends on the quality of the exciting y rays
and also upon the nature of the scattering medium. The qualities
of the incidence and emergence radiations are not always identical.
Cooksey (Nature, Ap. 2, 1908) worked in like manner with
the corpuscular secondary radiations from Rontgen rays,and brought
his results into parallelism with those for y rays; although the
asymmetry was very much less pronounced, R varying from 1:1
to 2 for different elements.
It remained for Brace and Guasson? to find a corresponding
lack of symmetry in the distribution of the secondary X rays
produced by the transmission of X rays through thin metal sheets.
The ratio & ranges from about 3 for Al to 1°3 for Pt.
Quite recently MADsENS has extended the enquiry to @ rays
and found very similar results. The greatest value of R is about
9 for Al and 45 for gold. He found that as the thickness of the
metal screen is increased, the total emergent scattered radiation
increases rapidly to a maximum (at ‘013 cm. Al and ‘0008 cm. Au)
and afterwards decreases,
With some of the foregoing results in mind the problem of
* Bragg and Madsen, Phil. Mag. 16, 1908, p. 918.
+ Madsen, Ib. 17, 1909, p. 423.
+ Bragg and Glasson, Ib. 17, 1909, p. 855.
§ Madsen, Trans. Roy. Soc. S. Australia, April, 1909.
270 Mr Kaye, The Emission of Réntgen Rays
the distribution of the Réntgen rays produced by the impact of
cathode rays on a thin metal target invited attack. The simplest
experimental conditions would be realised by the use. of as thin
a metal anticathode as can be obtained, and by employing cathode
rays of uniform velocity. This latter condition is being satisfied
in experiments now in progress, but as the cathode rays in soft
coil-driven Rontgen ray tubes are not very heterogeneous it seemed
worth while to carry out preliminary experiments in which the
condition of homogeneity of the cathode rays was waived. More-
over it has to be remembered that the Réntgen rays emitted will
be diluted to some extent with secondary Réntgen rays produced
by the action of the primary X ray beam on the material of the
anticathode. It remained to see what effect this would have on
the distribution of the primary rays.
mig mae
Anode
a j | y Ga Ee:
JAA! Anticathode i :
window
tT Zoe ue
Zane
J,
Apparatus.
The apparatus is sufficiently indicated by the figure. An
anticathode of thin metal leaf was mounted centrally in the
tube DH, so that it could receive a pencil of cathode rays from
either side at an angle not far removed from the normal. The
X rays produced could pass out normally by the aluminium windows
D and £ which, needless to say, were equally thick (‘01 cm.).
The idea in providing two cathodes C and C’ was to guard against
any possible want of symmetry in the apparatus. Plane cathodes
had to be employed; such thin leaves as were used for anti-
cathodes puncture at once if any attempt is made to focus the
cathode rays. The tube was coil-driven.
~ from Thin Metallic Sheets. 271
The intensity of the X rays was measured by an ionisation
chamber J (with thin aluminium bounding walls), and a Wilson
electroscope: the usual insulation and shielding precautions were
taken. If the rays were cut down by a screen, it was, of course,
- inserted between the aluminium window and the ionisation
chamber.
The anticathode was earthed and put in metallic contact with
the tube-anode A or A’. The whole of the discharge tube could
be slewed round by means of the mercury-trapped ground-joint J,
which led also to the pump. Thus the X rays proceeding from
either window could be measured by the one ionisation chamber :
one had only to rely on the constancy of the discharge.
Results,
: Thickness of | « 3 Thickness of Emergence Rad.
Anticathode Anticathode SHEE (ei Al. Screen ~ Tneidence Rad.
-1 em. None bei)
= 022 cm. 1-25
; 3 ‘Son i. 1335)
00001 em. f ee 1-50
-) em. None 1:30
718) ge s 1:40
Gold ‘D em. None 1:00
us 047 cm. 1:00
00002 cm. 1-5 cm. None 1:25
3 022 cm. 1:35
A 047. ,, 1:50
: ‘5 em. None 0-90
HUUUE ORL | Te one 1-05
"1 cm. None 1°30
2» %9 1-90
RS ‘022 cm. 2°00
00001 cm. ‘7 cm. None 3°20
Aluminium zB Vecion ee
vem: None 2°50
5 ‘047 cm. 2-00
; CICarey ts None 2-80
00002 cium. leas Wage 3-10
Copper |*000042cm. “2 em: None 1:10
272 Mr Kaye, The Emission of Réntgen Rays, ete.
In these preliminary experiments, aluminium, copper, gold
and platinum leaf were used for anticathodes. A few typical
measurements of the ratio R of the intensity of the emergent to
the incident radiation are appended. Platinum behaves like gold
in the values that it yields for the ratio under different conditions.
The speed of the cathode rays, being dependent on the potential
between the cathode and anode, is sufficiently indicated by the
length of the alternative spark gap (between large brass balls).
These and other results indicate the following points :—
1. Generally speaking the emergence Réntgen radiation from
a thin metal anticathode exceeds the incidence in intensity. This
is most marked in the case of aluminium. Furthermore, as evi-
denced by the phosphorescence of the glass walls of the tube, the
accompanying emergence secondary cathode radiation from the
anticathode is more intense than the incidence cathode radiation.
As far as could be judged “Rk” for the cathode rays seems to
follow any variation of “R” for the X rays. Madsen’s results
(above) for 8 rays may be noted.
2. With heterogeneous cathode rays the incidence beam of
Rontgen rays is softer than the emergence.
3. The ratio (#) of the emergence intensity to the mcidence,
increases with the speed of the impinging cathode rays, provided
the anticathode is thick enough. This is shown both by increasing
the potential on the tube, and by sifting out (with screens) the
softer X rays produced by the more slowly moving constituents of
the heterogeneous bundle of cathode rays.
4. For each thickness of anticathode there is a certain speed
of cathode ray which gives a maximum value to the ratio R. The
ratio drops in amount for greater or less speeds than this.
5. As the thickness of anticathode increases, the emergence
intensity (for the same speed of cathode ray) first increases to a
maximum and then dies away; the incidence intensity meanwhile
gradually increases to a constant value. The resemblance to
Madsen’s results for 8 rays (above) will again be noticed.
A discussion of the results is reserved until the measurements
are concluded.
I wish to thank Sir J. J. THomson for his interest in these
experiments.
Mr Crowther, On the Scattering of B-rays, ete. 273
On the Scattering of the B-rays from Radium by Air. (Pre-
liminary Note.) By J. A. Crowruer, M.A., St John’s College.
[Received 18 August 1909. ]
In a previous paper* I have described some experiments on
the scattering of a beam of the @-rays from Uranium by thin
sheets of various solid substances. It was shewn that a very
thin sheet of metal was sufficient to produce almost complete
scattering in a narrow pencil of P-rays; and further that the
diminution in intensity of a definite pencil of rays due to
the scattering of the rays, might be expressed by an exponential
law.
The present paper contains a brief preliminary account of
some experiments, still in progress, on the scattering of a beam
of 8-rays from Radium during its passage through Air.
A pencil of @-rays from Radium is spread out into a magnetic
spectrum, a portion of which, consisting of rays having a definite
small range of velocities, falls on a small aperture in a lead
sereen. The rays passing through this aperture are further
limited by a second screen, so as to form a narrow divergent
pencil of small angle consisting of rays of very nearly the
same velocity. The intensity of the @-radiation passing through
the geometrical cross-section of this pencil, at various distances
from the origin, is measured by the ionization produced in an
ionization chamber. It has been found that if J, is the initial
intensity of the pencil of @-rays, and J the intensity passing
through the geometrical cross-section of the beam at a distance d
from the origin, then
Jf = yg Sok.
where o is a constant, which may be called the coefficient of
scattering.
The following table gives the values of o for ordinary air
Velocity (em./sec.) | o« (em.—) v.No (1 — 82)-4. wo
| 2:26 x 10% "255 LOO es reo Se a2
2-50 134 151 2°03
2-74 072 1:42 2°23
2°84 ‘040 1:27 2°23
* Proc. Roy. Soc. A, Vol, 80, p. 186. 1908.
274 Mr Crowther, On the Scattering of B-rays, ete.
for various velocities of the @-rays. The first column of the
table gives the velocity of the rays employed, as calculated from
their magnetic deflection; the second column the corresponding
value of o, the coefficient of scattering for air at normal temperature
and pressure. The third column gives the value of the product
v/o, where v is the velocity of the rays employed. It will be
seen that the coefficient of scattering of the rays varies rather
more rapidly than the inverse fourth power of their velocity.
This is probably due to the increase in the electrical mass of the
8-corpuscles with increasing velocity. Prof. Sir J. J. Thomson *
has shewn that the coefficient of scattering is roughly propor-
tional to 1/v'm?, where v is the velocity and m the mass of the
8-corpuscle. Assuming the Lorentz formula for the change in
mass of an electron with change of velocity, we have
m=m, {1 — B73,
where £ is the ratio of the velocity of the corpuscle to the velocity
of light. Taking into account, therefore, this change of mass with
velocity we should have
(1 — 62)" *.v. /e = constant.
The last column of the table, which gives the values of this
quantity, shews how far this is the case.
* See Conduction of Electricity through Gases, p. 377. 1906.
Mr Vegard, On some general Properties, etc. 275
On some general Properties of Mixed Solutions. By L. VEGARD,
Universitets-stipendiat of Christiania University.
[Received 9 June 1909.]
INTRODUCTION.
§1. The object of the following paper will chiefly be to
generalise some results concerning properties of solutions, which I
have given in a previous paper*. The results found in this paper
were, in short, the following :
I. Determination of the variation of concentration in a binary
solution exposed to any field of gravity.
(a) Applying a purely mechanical equilibrium condition, it
was proved that the concentration in the equilibrium state must
be constant along an equipotential surface and have its greatest
slope in the direction of the force.
(6) The concentration gradient was found from the condition
that a small volume element acted on by gravity shall be in
thermodynamic equilibrium. The result found holds good for
any concentration and without regard to the volatility of the
compounds.
(c) In the case in which the osmotic pressure is known as a
function of concentration, the concentration gradient can be found.
Numerical calculations were carried out for cane sugar under the
assumption that the osmotic pressure follows the gaslaws. In the
case of electrolytes, the equation had to be slightly modified, and
the calculation was carried out for potassium hydrate.
II. (a) Using the conception of osmotic pressure, some very
interesting relations were found connecting the concentration
gradient with the variation of osmotic pressure with hydrostatic
pressure. These relations were:
1 /d7\ dec Or
(1) p—p=R(a) ay t Paw
1 /dr\ de Om
(2) p— =e (a) ant Poa
Or Om Om
Or int a
p is the density of the solution at pressure p; p) that of the
solvent at p); 7=p—p,=osmotic pressure, p and p, being the
* «Beitraige zur Theorie der Lésungen.” Christiania Vid. Selsk. Skr. No. 8,
1906. Phil. Mag. [6] 13, p. 589, 1907.
276 Mr Vegard, On some general Properties
pressure on the solution and solvent respectively. The relations
(1, 2, 3) are quite general for binary solutions. They hold for any
concentration without regard to volatility of the compounds, and
the fluids may be compressible.
(0) As a corollary from the three equations it was found that
dc dc
of osmotic pressure with concentration will be different according
as the pressure during the variation is kept constant on the
solution or on the solvent.
The problem we shall deal with in the following is to find the
distribution in a solution contaiming an arbitrary number of sub-
stances acted on by any field of gravity, provided equilibrium has
set in and the temperature is constant all through the system.
We shall treat the problem in two ways: in one we shall use
the thermodynamic potentials, in the other we shall make use of
the conception of osmotic pressure. But as the osmotic pressure
up to the present has only been defined for binary solutions, it
will be necessary to extend it to solutions in general.
in general (=) and (=) must be different, or the variation
DP Po
Part I.—Solution of the problem by means of
thermodynamic potentials.
§2. Some properties of thermodynamuc potential functions.—Let
the solution be composed of (7 + 1) substances 0, 1, 2 ... 7, with mo-
lecular masses V/,, M, ... M,, and let the concentration be measured
by the number of gram-molecules in unit volume 7, 7,2... My,
which in the case considered will vary from one point to another.
In the following the concentrations as well as their first derivates
will be considered as continuous functions of the coordinates. In
the case of varying concentration, the thermodynamic potentials
of the solution will no longer be homogeneous functions with
respect to the total mass of each component; but we must be able
to assume, considering the thermodynamic potential Aw for a
volume element Av, that when Av approaches zero A@ will
approach the value it would have if the element had contained a
homogeneous solution with concentrations equal to those at any
point inside the element. Thus we can put
Ao= H (Am, Am,, Am, ... Am,, p, T),
where Am,, Am, ... Am, are the masses inside the element and H
is the same function as in the case of a homogeneous solution. Tis
the temperature, which is supposed constant, p the pressure on
the element. Putting Am;=/;n;Av:
Aw
Lim AG w= A (Min Mine. Monet pL);
of Mixed Solutions. 277
w' is the thermodynamic potential per unit volume at the point
considered. The thermodynamic potential for the whole system
= || [ o'dedyde
w' being a homogeneous function of the first degree*,
(5) ow =f\Mont+AMn +... f,- Mn,
= hom + him +... hyN;.
fi, fi--- fy ave the thermodynamic potentials per unit mass of
the various components.
~,¢;-..$, are the thermodynamic potentials per gram-
molecule of the various components, and
(6) Mi fi=gi= S
¢; being homogeneous of degree 0 with regard to n,n, ... 0;,
(7a) ee = (0),
s=0 07 8
and since
Opi a Ops
(7b) Ons a On; 2
S=T Obs ot
(7c) 2 On; Ng = Vv.
Let w be the thermodynamic potential for constant pressure.
Then
/
do
(8a) Apia ame) =e
or by means of (5)
(8b) Spins=1,
0
where y; is the molecular volume of the component (2) under the
conditions present. Let 6n,, 6n,... dn, be simultaneous variations
of m,,n,...n,. Then from (8b) and (7a)
(9a) S ui 8n; =\)
0
The expression to the left in equation (8b) is a function of
(xyz), and its total differential must be equal to zero, but as (#yz)
are independent variables, the partial differentials with regard to
* See Duhern, Mécanique Chimique, tome 111. livre v1.
278 Mr Vegard, On some general Properties
x,y and z must be equal to zero. Then differentiating equation
2
(8b) with regard to #, and remembering that ih)
op
dn;
Syma eS
Taking the variation of the equation (9b),
A CAEN AVS OG Os SEG
6(——}+ = = > +“dn,=0;
Suid (a) ap Le earls ong = 0;
but the last term is equal to
Sau Oe =o ean.
> 6n,— > ps = =
s=0 ONsj=9 &
0,
then
a dn;
SS ie cee Nae
(9c) = i 8 (F) 0.
$3. Thermodynamic equilibrium conditions.
As is well known, the condition for thermodynamic equili-
brium at constant temperature can be expressed
be =(64)a,; .
(OW )az = (84 Jas,
were ees ears erereccen
(10)
\(Sy)a,, = (BA)a,
a is the internal thermodynamic potential =7+ST7, where J is
the internal energy, S the entropy. 6A is the work done during
the variation by the external forces acting on the system. The
equations (10) express that for any independent variation the
system may suffer the change in w must equal the work done.
The equilibrium of our fluid system is not disturbed if we
assume that a closed surface is laid inside the fluid and this
surface becomes rigid. Moreover, the equilibrium is maintained
if we imagine that an element of the surface is replaced by a
movable piston pressing against the fluid with a pressure P equal
to that existing in the fluid at the element considered. Thus we
are quite free as regards choice of bounding surface.
The field of gravity to which the system is exposed we shall
assume depending on a potential U, where U, as well as its first
derivates, are supposed to be continuous in the space occupied by
the system.
Now we get
5(4)=- P8 ff] dedydz ~ 8 {|| p Udedyde,
-
of Mixed Solutions. 279
and by means of (4) the equilibrium condition can be expressed
8 [| [ Cy + pU + P) dedyde=0,
or introducing the thermodynamic potential for constant pressure w’
3 {|| (o +pU+ P—p)dadydz=0.
The variation must be subject to the condition that no mass
leaves the boundary. Putting
GL) Gr abe Oey We
we get the equilibrium conditions
(12a) 8 | i il Wied ern
(126) 8 [| [nc dedyde = 0, 4=0,1,2...7.
(12c) 8 [[[paedya: = 0.
(12c) is of course a consequence of (126).
§4. Solution of the problem of variation.
We shall now specify our bounding surface; and, as we have
seen, this can be done without restricting the generality of the
solution. We shail consider the fluid inside a parallelopipedic
element (Aw, Ay, Az), and, for the sake of simplicity, one of the
corners may be at the origin of the coordinates. Further, we shall
let the element have a needle form, or we put
Ag =a, Aa, Az—a, Au,
where a, and a, are finite quantities and m, and n, are positive
numbers, which can be given any values we like, and thus we can
always be able to put
nm, =2 and n, = 2.
The two ends of the element we shall denote by (0) and (1). The
element is supposed to have rigid boundaries except at the end,
which consists of the piston exerting a pressure P.
We shall specify the variation, which consists in a relative
displacement of masses inside the element, by supposing that
the masses are suffer a translation parallel to the principal axis of
the element. Under these conditions the equilibrium conditions
take the form
VOL. XV. PT. III. 19
280 Mr Vegard, On some general Properties
( Ax : Ax
af Wis 0” Wen s | 3 Wde,
0 0
| Az pAa
(13) [ “mde =0= f(A) + “dudz, i=0,1, 2.0.7
0 0
PAG Aa
al. nds ee) I. Sake
W,, ni, p, are the values of W, n; and p at the end (1) of the
element. We develop the functions W,n; and p after Maclaurin’s
formula, and, forming the variations, we get
sW=5W.+3(5) z+ ete,
k 0
dn; =dn?° +8(F =) « + etc.,
5p =3p,+8(P ) e+ ete
These values put into (13), and integrating
(l4a) W, eS + 48(), Ag+ ...=0,
(14b) ni oes p+h 5 (S). Ae+... =0, ¢=0,1,2...7.
§(Az) dp ‘i
(Ide) pr po + 49(72) Ananth aly
To find 6(Az) we shall apply equation (14b); we multiply
with yw; and add
r
(15a) Jie aS = pi Me +3 pi (dng + $6 (=) Nake )=0.
0 0 0
fi is the ae of yw; at the end (1),
, dp;
Gis, Un Rae BC
Bi = pet = AG + oe.
Putting the expression for y,/ into (15a), and using the equa-
tions (8b), (9a) and (9c),
8(Az) oe) a = eee at
i + Aw = ( (dn! +4 lee Act... =
Using equation (140)
8(Az)
Ag
(15d)
os — Az 5 Hin) aha +...,
6. dz
of Mixed Solutions. 281
where a is a quantity containing some linear relation of the form
dn;
= , p=2. We may at once remark that if the value for
6 (Az) is put into (14) and we go to the limit Aw = 0, we find that
the term depending on 6 (Az) disappears.
From equation (11) we get
dW, = da, + U,dpo,
AGe leah Gata) Gas
p. being the pressure at the bounding surface is not altered by
the variation. Putting these expressions into (14a) and using
(14c) and (15)
(16) 6d, +4 {3(%2) + aka — 6 (2), Az + etc. =0,
where ete. is of the form a,Av% + a,Av?+...9¢ $2.
From equation (5)
Bay’ = 3 $P8ni,
ste) 0 (1) ace (8) $0 a
Putting the expressions for de,’ and 6 es into (16), and
0
using (146) the equilibrium conditions take the form
(=), Sepia : (=), 862+ ¢Ax +... =0,
d
or letting Aw converge ae Zero
(17) o 8p i co. ae H 86;= 0.
We drop the index (0), and ee that all values refer to
the same point
dp = = M,N
These values put into (17) give
(18) 3 (a Ue Od; 2) Sn,
s=0
© dx *j=9 On, ax
19—2
282 Mr Vegard, On some general Properties
or putting for brevity’s sake
aT 2=" Od; dn;
is Gg +E, am de =
and remembering equation (9a)
(19) ee + Q,6n, +... Q,6n, = 0,
My ON) + po, ON +... fy ON, = O.
The equations (19) must be fulfilled for any variation én; con-
sistent with the two equations, then
Qo Qr _ =
20 SSeS =... = => Oss.
ey) Mo fa by 0 (sm
Forming by means of the expression for Q, the sum to the right,
z dU
= Qans a Cds
The equations (20) and (9b) then give
Ody Any 0d, dn, me dn, By a.
On, dz On dx cas on, dz du (opi Mh) ae
0ddn, dd,dn, 0p, dn, ae
on, dz dn, dx Soe (om U2 1,
(QIN eed Se ee ech ee
Ado An Op, diy Od, dn,
On, dz | On,dx On, du da ~ (eptn — Mya = 2.
We have here apparently (r+ 2) equations between the (r+1)
ao diy; ay,
da’ dx’ dx
the following linear eas exists
Kyomt+ Ayn t+... Bn, = 0.
The solution of equations (21) gives
unknown ; but they are not all independent, in fact
COR eS Gh)
dx Date
and for the other axis
dn; 29): dU
dip Ga
dn; 7, dU
dz a D; az ?
and (22) dn; = D,dvu.
of Mixed Solutions. 283
Thus we see that also in the general case the concentration in the
equilibrium state must be constant along a potential surface, and
for the same concentration pressure and temperature the con-
centration gradient will be proportional to the force intensity at
the point considered.
The equations (21) determining the concentration fall in any
direction are perfectly symmetrical with regard to the (r+1)
components. The solution found holds regardless of compressi-
bility of the solution and of the aggregate form of the single
components, and for any concentration whatever, that may have
physical existence.
§5. Transformations.
During the theoretical development we have assumed that the
concentration is defined as the number of gram-molecules per unit
volume. There are, however, several other ways of expressing the
concentrations, and it may be useful to find the expression of our
equation system corresponding to the most usual forms of concen-
tration.
1. The concentration is defined as the mass of each component
contained in unit volume. Let us call these concentrations
CrCe... ©, then
C; = M;n;. 4=0, We Dies 15
Introducing b= UM; fi,
yaa
and 1; Gis
OU 00) a dan nee
dC, aC, aC, _
2 ap a a Pa
af: dC, . af; dC, af, dC, dU
as!
qi is the volume which unit mass of the component (2) occupies
in solution under the conditions present.
2. The concentration is given as the amount of mass of each
component contained in unit mass of solution. Call these con-
centrations o), 0,...0,, then
Employing well-known rules for transformation
00) 02) NOG at). | Conan
= (ou: — 2), i=0,1,2...7.
(24)
284 Mr Vegard, On some general Properties
3. We choose one of the components, e.g., the first one as the
principal component, and we express the concentrations of the
others by the ratio between their masses and that of the principal
component, all masses being united in the same volume element,
or
eer ee
Ceti? ThOniia mess
We have
de ~ det de
of; Bohs OC, , Si Os cs Ofi 0c,
OCh mac GO, nmoGroCne anor. Un
Of: _ Of; Oes eae
00, acs 005" ° > eae
Forming the expression in equation (23) and putting
qip —1=4;,
we get the following system
SearUjfe Gs once Sd
(25) foie ar ae OEE: . ¢= 0), 2am
In this case there are only 7 concentrations, and consequently
runknown. If we drop the first of the (7 +1) equations (25), we
get the following solution
Gji Of, 9 Of ays Of, Of. nl tOpa : of. of
OC, OC.” OC; ** OC» OC, 06; | OC; OGeeawn 106s
Afr fo fe Ofe Of Of hey Of. Os
OC 00.4) OG: au OG, OC, 06, °~ ace : are fT O68
(26) Re : hd Webey hive Gah sige : :
Fi of Ff af, |de de | of, of; 7 Of: afi
08 00, "Oc; OCp 00, 002 Bei" Gnk oes
af. OF Sf ofr af, af Sr ofr
Ulin Gis neal 0c, OG, OC *OCia4 OG
de;
To find ae we must know the 7 quantities a,a...q@,, and,
besides, a number of quantities derived from the thermodynamic
potentials. As we have
“Be, mr ;
of Mixed Solutions. 285
the determinant to the left is symmetrical, and the number of
thermodynamic quantities reduces to $r(r +1). For a binary
solution we get the very simple result
In the earlier paper* the quantity gq, is found for binary solutions
Loe eee a
Mu, © = 2 prac +e) | >
af, do, _1
de, da = p2' S36, dar’
and
which is the same result as that found in the previous paper.
Part Il.—£atension of the conception osmotic pressure
to solutions in general.
§6. In the previous development we have seen that the
thermodynamic potentials are very apt for a general mathematical
treatment. The thermodynamic quantities appearing in the
equations are mathematically very simple, all of them being
derived from a single function by means of a simple mathematical
operation. In spite of their mathematical simplicity, the thermo-
dynamic potentials have their disadvantages when we are trying
to get a clear idea of what they contain physically, and their
interpretation is in fact the important thing when we are going to
utilise them in any special case. Here it is that the importance
of the osmotic pressure comes in; and even if we consider the
thermodynamic potential to be the basis for the theory of solu-
tions, the generalisation of the conception of osmotic pressure will
still be of importance for a general treatment of solutions. The
equations connecting the osmotic pressure with the thermo-
dynamic potentials are from one point of view to be regarded as
equations defining the osmotic pressure, but will at the same time
give a physical interpretation to the thermodynamic functions.
The conception of osmotic pressure may be generalised in a
number of ways; it will be our task to find the most useful. Let
the solution, as before, consist of (r+ 1) substances, and suppose
that we have a membrane permeable to (i) of them but imper-
meable to the rest. The solution may be supposed to be con-
tained in a cylinder and the membrane to have the form of a
piston. We imagine that there is at first no fluid above the piston.
If we apply a pressure sufficiently high, some substance of the (7)
* Phil. Mag. [6] 13, p. 599.
286 Mr Vegard, On some general Properties
components will pass through, formimg above the membrane a
solution, which we may call the secondary solution of the osmotic
system. By diminishing the pressure, the current through the
membrane will be less, until for a certain pressure an equilibrium
will set in. There will be (2) equations determining the equili-
brium state ; from these the (7 — 1) concentrations of the secondary
solution, as well as the osmotic pressure, will be determined.
When the osmotic pressures are derived in this way we shall say
that they are formed upon a given solution.
The number of osmotic systems that can be formed upon a
solution is
ees eee
j=1 U! (r-—74+ 1)!
Roria, binarysolutromye sees mcs oe eee if =
For a solution containing three components... NV = 6.
For a solution containing four components ... V=14
For a solution containing five components ... WV = 30.
The most important of these systems are those we get for 7=1
and 7=r.
§7. The partial osmotic pressure.
When the membrane is permeable to all but one component,
we get an osmotic pressure which is analogous to the partial
pressure in a mixture of gases; we may call it the partial osmotic
pressure for the component considered.
Let the membrane be impermeable for the component (7), and
/ / ,
let c, = Toy, — aia eet ar ie “= be the concentrations at the
My My My
secondary solution. The equilibrium conditions are expressed by
the equations
EG) Fak. i=0, 1) 2... .@ =m
Fi =F i (G, G...¢, P) = thermodynamic potential per unit mass
of component (7) in primary solution.
Fi =F (a, Cy ..-C'r_y, 0, p, I= thermodynamic potential per unit mass
of component (7) in secondary solution.
P the pressure on the primary, p, that on the secondary solution.
If c,c.... ¢,, P are supposed to be given, the 7 equations (28) de-
termine the r unknown ¢,¢) ...¢’,-1,pr- What interests us is
the osmotic pressure Q, =(P —p,).
In order to get a nearly exact expression for this pressure we
shall assume that in the state of equilibrium the differences
c;—c; are small quantities; or, that the substances for which the
of Mixed Solutions. 287
membrane is permeable have nearly the same mutual proportion
on both sides of the membrane. On this supposition, neglecting
quantities of second order :
s=r-19 ms ,
fi =fit+ = O(c, —¢s),
s=1 OCs
where hE (Gm Ca iG pai. One):
We multiply the equations (28) with 1, c,, c,...c,_, in succes-
sion and add them together, and inserting the value for /;’
r-1 i s=r—1 41=r—1 Of;
@9) 2(i-fya= = @—¢) > 4G,
0 s=1 on GGs
where we have to remember that c,=1. From equation (7a) we
get
t=r-1 Of: a
7=0 OC; as ‘
From a well-known property of thermodynamic potential
afi
ap = qi where q; is the volume occupied by unit mass of the com-
ponent (2) in a solution of the same substances as the secondary
solution, but with concentrations equal to those of the primary one
Creer. Ca,. Lhen
P
BA Gis Cy is- Cr-1,9, Te) a (Cr Cras Ge, Os D,) = ang p:
Dr
HEA GrG sere Cpeanga Cys) ly (Ci5.Cp > Cyn Oyek) =|" = de,.
0 T
Adding these two equations together
° ’ Cr é t 1B D
fess: -| Hi ae, + | qi Up.
0 OC, Pr :
Inserting into (29)
(30) pees? oo) dey = -[ (“Eaiei) dp,
i=0 pr \ 7=0
i=r- :
Z=() 0c, 0c, i
where V’ is the volume of a solution with concentrations
(1,0... Cr and (7m)” the amount of mass of the component (0)
contained in the same solution.
19—5
288 Mr Vegard, On some general Properties
Equation (30) then takes the form
line’ a
“y? dp me ma, Ld,
Pr
In general we have
Gay Mm;
ie eco RISE 1=0,1,2...(r=—1).
[va iy My ie wane
Pr om,
0
Taking the sum of these equations from 7=0 to t=r—1,
r—1 r—-1
= (m)’ =m
0 sae 0
P r My 4) 2
V' dp | My Sr dm,
Dp 0 Om,
i Vv’ ; i
but = 2 Sear = specific volume of a solution of concentrations
CCRC, a and IMtrod Tene
My
My + My +... Mp4”
the osmotic pressure will be defined by the equation
. Tea ash Wye Siar
(31a) ls doe I K, Oe dK,
Gs
ie 28 i 2
If —, is the mean value of i in the interval P —p, we get for
m
the osmotic pressure Q,
(316) Q = pall Kx ae os
This expression is well known for ace solutions, and we see
that with a proper modification of the quantities pm, K, and f,
the same expression holds for the partial osmotic pressure.
§ 8. Osmotic pressure of the first order.
When the secondary solution only contains one substance, we
shall designate the corresponding osmotic pressure to be of the
first order. Let 7; denote the osmotic pressure, when the mem-
brane is permeable to the substance (2). From the {condition of
equilibrium we get in the usual way
: Pil
32 ie =| = a ae
(32) mers evi: = if;
of Mixed Solutions. 289
f; = thermodynamic potential per unit mass of component (2) of
the solution at pressure P;.
gi = thermodynamic potential per unit mass of pure substance (7)
at pressure P;.
p; is the density of the pure component (7), and p,,; its mean value
between P; and p;.
Partial derivation of (32) with respect to c; gives
OF; Ci, C airs de 1 OT;
(33) OL; (Cy Co +++ Cry Ps) = ( ) i
P;
OCs i Pmi OCs
Assuming that the pressures on the solution P; are the same
for all osmotic systems and equal to p, the equation (33) will give
an expression in terms of osmotic pressure for all the thermo-
dynamic quantities appearing in equation (26).
From the equation (27) we get the following relation
i 1
Ga (=) wi (=)
Pmi \ OCs p Pms OC; p
This interesting reciprocal relation between the osmotic
pressures of the first order, which is a simple corollary from their
connections with the thermodynamic potential, would have been
very difficult to obtain from a separate consideration of the
osmotic pressures themselves.
Part III.—The effect of gravity upon solutions found by
means of the osmotic pressures of the first order.
§ 9. The osmotic pressure of the first order enables us to
generalise equations (1) to solutions in general, The method
used in the previous paper only needs to be slightly modified.
Instead of only one, we have to form (r) systems, which we get by
supposing the solution successively in osmotic equilibrium with
the 7 substances 1, 2...7, which, at the temperature considered,
all are supposed to be in the liquid state. Moreover, we must
assume that in the state of equilibrium the pressure in the solu-
tion is the same for all osmotic systems.
Using the same way of reasoning as before*, we get
SOT, OCs, o7;\ dU
5) 3 Ge) gen (Pme +P ae) de
= er
= and a mean here the variation of U and ¢ per unit length
* Phil. Mag. [6] 13, pp. 607, 608.
290 Mr Vegard, On some general Properties, etc.
from a point on the surface of the membrane and along some
direction in this surface, but as the direction of the surface is quite
arbitrary, the increment dz may have any direction whatever.
From equation (32) we get
OT;
Op
: SSL (Gam ake: dU
(36) 2% ~ (om) Ape (l—pq) G--
s=1 Pi des p da S
VERA sos, UP
If we transform this system of (7) linear equations by means of
equation (33) we get the result expressed in equation (25), show-
ing that the osmotic method leads to the same result as that in
which we used the thermodynamic potentials.
There is, however, one difference between the two solutions of
the problem. In order to apply the osmotic pressure method, we
had to assume that the 7 components were in a liquid state; the
treatment with thermodynamic potentials only requires that the
solution is fluid at the temperature considered, and the components
may have any aggregate form whatever.
Putting the value for into (35)
§ 10. Summary of results.
(1) Applying the general thermodynamic equilibrium condi-
tion, the variation of concentration caused by any field of gravity
is found for a solution containing any number of substances, and
the result is expressed in terms of thermodynamic potentials.
(2) The conception of osmotic pressure is extended to a solu-
tion containing any number of substances.
(3) Simple expressions in terms of thermodynamic potentials
are found for the partial osmotic pressure and for the osmotic
pressure of the first order.
(4) By means of the osmotic pressure of the first order we ob-
tained a physical interpretation of the thermodynamic quantities
ofi
OCs"
reciprocal relation was found for the osmotic pressure of the first
order.
(5) The osmotic pressure of the first order gave us a simple
way of finding the influence of gravity upon a solution.
From their connection with the thermodynamic potentials a
FP
PROCEEDINGS AT THE MEETINGS HELD DURING
THE SESSION 1908—1909.
ANNUAL GENERAL MERTING.
October 26th, 1908.
In the Optical Lecture Room.
Dr Hosson, PRESIDENT, IN THE CHAIR.
The following were elected officers for the ensuing year :
President :
Prof. Sedgwick.
Vice-Presidents :
Mr S. Ruhemann.
Prof. Thomson.
Dr Hobson.
Treasurer :
Mr H. F. Newall.
Secretaries :
Mr A. E. Shipley.
Dr Barnes.
Mr A. Wood.
Other Members of the Council :
Mr F. G. Hopkins.
Mr A. Harker.
Prof. Larmor.
Dr Duckworth.
Mr W. G. Fearnsides.
Dr Sell.
Mr W. E. Dixon.
Prof. Wood.
Prof. Hopkinson,
Prof. Seward.
Dr Fenton.
Mr G. H. Hardy.
292 Proceedings at the Meetings.
The following was elected a Fellow of the Society :
G. N. Watson, B.A., Trinity College.
The following Communications were made:
1. Note on Russo’s attempt to show differentiation of sex in the
ovarian ova of the Rabbit. By W. Hare, M.A., Trinity College.
2. <A further note on the eggs of the hermaphrodite Angiostomum
nigrovenosum. By 8. A. M°Dowatt, M.A., Trinity College.
3. Plemelj’s Canonical Form. By J. Mercer, B.A., Trinity College.
4. On Monotone Sequences of Continuous Functions. By Dr
Youna.
5. The Operator Reciprocants of Sylvester’s Theory of Recipro-
cants. By Major P. A. MacManon.
November 9th, 1908.
In the Cavendish Laboratory.
ProFessor SEDGWICK, PRESIDENT, IN THE CHAIR.
The following were elected Fellows of the Society :
J. Pope, M.A., Professor of Chemistry.
A. Henry, M.A., Reader in Forestry.
The following Communications were made:
1. The positive ions given out by hot wires. By Professor
THOMSON.
_ 2. The weight of a corpuscle on the electrical theory of gravitation.
By Professor THomson.
3. Note on the distribution of electric force along the striated
discharge. By Professor THomson.
4. Note on the Radio-activity of Rhubidium. By N. R. Campsett,
M.A., Trinity College.
5. The free pressure under osmosis. By L. Vecarp. (Communi-
cated by Professor Thomson. )
6. The Laws of Mobility and Diffusion of the Ions formed in
Gaseous Media. By E. M. Wettiscu. (Communicated by Professor
Thomson.)
Proceedings at the. Meetings. 293
‘November 23rd, 1908.
In the New Medical Schools.
ProFrEssoR SEDGWICK, PRESIDENT, IN THE CHAIR.
The following were elected Fellows of the Society :
V. H. Mottram, M.A., Trinity College.
G. R. Mines, B.A., Sidney Sussex College.
The following Communications were made :
1. The relationship between human and bovine tuberculosis. By
Professor WOODHEAD. - sole
2. The transmission of Trypanosoma lewisi by fleas and lice. By
Professor NUTTALL.
3. The presence of anticoagulin in the salivary glands of Argas
persicus. By Professor NUTTALL.
4, The mode of action of specific substances. By W. H. Dixon,
M.A., Downing College, and P. Hamit, B.A., Trinity College.
5. The action of specific substances in toxaemia. By W. E. Dixon,
M.A., Downing College, and W. H. Harvey, B.A., Christ’s College.
6. Therapeutic Inoculation for generalised bacterial infections.
By L. Noon, M.A., Trinity College.
7. A simple method for examining leucocytes. By C. Ponpmr,
M.A., Emmanuel College.
8. The mode of growth of bacteria. By Dr Granam-Smirn.
9. The radiation of neon in a strong magnetic field. By J. E.
Purvis, M.A., St John’s College.
10. On the effect of Pressure on the ionization produced by
Roéntgen Rays in different gases and vapours. By J. A. CrowTHER,
B.A., St John’s College.
11. On the variation of the relative ionization produced by
Rontgen Rays in different gases with the hardness of the rays. By
J. A. Crowruer, B.A., St John’s College.
12. Waves in a stream of viscous liquid. By W. J. Harrison,
M.A., Clare College.
January 25th, 1909.
In the Cavendish Laboratory.
Proressor Sir J. J. THomson, VickE-PRESIDENT, IN THE Cnatr.
The following was elected a Fellow of the Society :
J. E. Littlewood, B.A., Trinity College.
294 Proceedings at the Meetings.
The following Communications were made:
1. A String Electroscope. By T. H. Lasy, B.A., Emmanuel
College.
2. Secondary Rontgen Radiation. By J. A. Crowrner, B.A.,
St John’s College. (Communicated by Professor Sir J. J. Thomson.)
3. Interference Fringes with Feeble Light. By G. I. Taytor, B.A.,
Trinity College. (Communicated by Professor Sir J. J. Thomson.)
4. The solution of Linear Differential Equations by means of
Definite Integrals. By H. Bareman, M.A., Trinity College.
February 8th, 1909.
In the Chemical Laboratory.
Mr 8. RuHEMANN, VICE-PRESIDENT, IN THE CHAIR.
The following were elected Fellows of the Society :
W. L. Balls, M.A., St John’s College.
W. H. Harvey, B.A., Christ’s College.
H. C. Haslam, M.B., Gonville and Caius College.
The following Communications were made:
1. Further studies on Dihydroxymaleic Acid. By Dr Frnton
and W. A. R. Winks, B.A., Gonville and Caius College.
2. Homologues of Furfural. By Dr FEnron and F. Ropinson,
B.A., Peterhouse.
3. Action of Urethane on Esters of Organic Acids and Mustard
Oils. By 8. Runemann, M.A., Gonville and Caius College, and J. G.
PRIESTLEY.
4. The absorption spectrum of a solid alkyl derivative of picene.
By Miss A. Homer and J. E. Purvis, M.A., St John’s College.
5. The absorption spectra of mesitylene and 3-chloromesitylene.
By J. E. Purvis, M.A., St John’s College.
6. The absorption spectra of concentrated and diluted solutions
of chlorophyll. By J. E. Purvis, M.A., St John’s College.
7. A coloured thio-oxalate. By H. O. Jonzs, M.A., Clare College,
and H. 8. Tasker, B.A., Emmanuel College.
8. Note on some double Fluorides of Sodium. By W. A. R.
Wixks, B.A., Gonville and Caius College. (Communicated by Dr
Fenton.)
9. Ona configuration of twenty-seven hyper-planes in four dimen-
sional spaces. By W. Burnsipr, M.A., Pembroke College.
Proceedings at the Meetings. 295
February 22nd, 1909.
In the Optical Lecture Room.
PROFESSOR SEDGWICK, PRESIDENT, IN THE CHAIR.
The following were elected Fellows of the Society :
J. A. Crowther, B.A., St John’s College.
H. H. Paine, B.A., Trinity College.
F. Shillington Scales, M.A., Jesus College.
The following Communications were made:
1. On the alleged influence of lecithin on the determination of
sex in rabbits. By R. C. Punnett, M.A., Gonville and Caius College.
2. Observations on the Changes in the Common Shore Crab
caused by Sacculina. By F. A. Ports, M.A., Trinity Hall.
3. Ona so-called “sexual” method of forming spores in Bacteria.
By C. C. Doss, B.A., Trinity College.
4. On the migration of the thread cells of Moerisia. By C. L.
Boutencer, B.A., King’s College.
5. A note on a specimen of Pelagothuria from the Seychelles.
By J. C. Simpson. (Communicated by Professor Sedgwick.)
6. The Study of Discontinuous Phenomena. By N. R. Campsett,
M.A., Trinity College.
March 8th, 1909.
In the Optical Lecture Room.
PRoFessor SEDGWICK, PRESIDENT, IN THE CHAIR.
The following was elected a Fellow of the Society :
G. Dixon, M.A., Trinity College.
The following Communications were made:
1. On the Nature of Anthocyanin. By Miss M. Wuenpate.
(Communicated by Professor Bateson.)
2. An Experiment on Ionisation with y Rays. By L. Vucarp.
(Communicated by Professor Sir J. J. Thomson.)
3. The Nature of the Ionisation produced in a Gas by y Rays.
By R. D. Kizeman, B.A. (Communicated by Professor Sir J. J.
Thomson. )
4. On Uniform Oscillation. By Dr Youne.
296 Proceedings at the Meetings.
5. On the parametric representation of the co-ordinates of points
on a cube surface in space of four dimensions. By H. W. Ricumonp,
M.A., King’s College.
6. The irreducible concomitants of two quadratics in variables.
By H. W. Turnsutt, B.A. (Communicated by Dr Barnes.)
May 3rd, 1909.
In the Botany School.
Dr Hopson, ViIcE-PRESIDENT, IN THE CHAIR.
The following Communications were made :
1. Ona specimen of the cone Calamostachys binneyana Carruthers,
By H. H. Tuomas, B.A., Downing College. (Communicated by
Mr EK. A. N. Arber.)
2. Note on two new leeches from Ceylon. By W. A. Harpine,
M.A., Peterhouse.
3. Note on an abnormal pair of appendages in Lithodbius. By
L. Doncaster, M.A., King’s College.
4. Ona property of summable functions. By Dr A. C. Drxon.
May 17th, 1909.
In the Cavendish Laboratory.
Proressor Sir J. J. THomson, Vick-PRESIDENT, IN THE CHAIR.
The following Communications were made:
1. Phenomena of X-ray Transmission. By C. G. Barkua, M.A.,,
King’s College. (Communicated by Professor Sir J. J. Thomson.)
2. Phenomena of the Cathode Discharge. By J. A. OrnanGE, B.A,
Trinity College. (Communicated by Professor Sir J. J. Thomson.)
3. Some fatigue effects of the Cathode in a discharge tube. By
R. Wurpprneton, B.A., St John’s College. (Communicated by Pro-
fessor Sir J. J. Thomson.)
4. The influence of dilution on the color and the absorption
spectra of various permanganates. By J. E. Purvis, M.A., St John’s
College.
5. Note on the Histology of the ‘Giant’ and ordinary Forms of
Primula sinensis. By R. P. Grecory, M.A., St John’s College.
CONTENTS.
Some fatigue effects of the cathode in a discharge tube. By R. WHID-
DINGTON. (Communicated by Professor Sir J. J. Thomson)... 183
Note on the electrical behaviour of fluorescing iodine vapour. By R.
WuHuIppiIneTon. (Communicated by Professor Sir J. J THomson) .
On the Reflection of Sound at a Paraboloid. ak the Rev... H. J.
SHARPE . 190 -
Discussion of a differe rence Sane ae 2 the tenston sf jueas
wires supported by equidistant poles. By A. A, RopB . “198
On a property of summable functions. By A. C. Dixon. - 210
On certain phenomena of the kathode region, By J. A. ORANGE. aun
_ maunicated by Professor Sir J. J. THomson). (Plates [V—IX)
Note on two new Leeches from Ceylon. By W. A. HarpIne . ‘ «32835
Note on the abnormal pair of centage in Lithobius. By F. G.-~ eo:
SINCLAIR : ~ = 285...
On a specimen of the-cone Calamostachys binheyane (Cases. )-. By H.
HamsHaw THomas.. (Communicated by Mr E. A. NEwWEnb =
ARBER) 236
Note on the Histology = the Gicmt aud hoe For MS of prraule sors
sinensis. By R. P. GREGory. (Plate X) 239
The influence of dilution on-the colour and the absorpeien. Spectra a b
various permanganates. By J. E. Purvis. (Plate XI)... .
Phenomena of X-Ray Transmission. (Preliminary Paper.) By C. G.
BarkLa. (Communicated by Professor Sir J.J. Taomson).
The Emission of Rénigen Rays from Thin Metallic Sheets. By G. W. C.
Kaye. (Communicated by Professor Sir J. J. Tomson) #269
On the Scattering of the B-rays from Radium by Air. (Preliminary
Note.) By J. A. CRowTHER . Feat ie 3
On some general Properties of Mixed Seluaon By L. a ; ees DIBA
Proceedings at the Meetings held during the Session 1908—1909 .
PAGE.
2
<5
q
; se
aS
ra
‘
2a
a
:
i
sso
217
947
DBT
273. 5
201.
Nii Sie ht
> 7 ty a Ges) ee
PROCEEDINGS
OF THE |
CAMBRIDGE PHILOSOPHICAL
SOCIETY.
VOL. XV. PART. IV.
[MICHAELMAS. TERM 1909.]
r=
Cambridge :
AT THE UNIVERSITY PRESS,
AND SOLD BY
DEIGHTON, BELL & co. AND BOWES & BOWES, CAMBRIDGE.
CAMBRIDGE UNIVERSITY PRESS,
C. F. CLAY, MANAGER, FETTER LANE, LONDON, E.C,
1910
Price Two Shillings and Siapence
31 January, 1910.
“NOTICES. eo
ag i ppleaion for scoala: sets of the (tek Saauaean ae
Volumes (in Parts) of the Transactions should” be made to. the =
Secretaries. of the Society.
2. Separate copies of certain pants of Volumes 1.—Xt, E the ee
Transactions may be had on application to Messrs Bowes. &
ae Bowns or Messrs DEIGHTON, ‘BELL & Co, Cambridge.
8. Other volumes of the Transactions. may be obtained at Se :
the following prices: Vol, xu, £1. 10s. 6d.; Vol. x. £1. 2s. 6d.;
Vol. x1v. £1. 17s. 6d.; Vol. xv. £1. 12s. 6d. 5 Vol. XVI. £1. 10s. Od.;
Vol. xvii. £1. 2s. 6d.; Vol. xvitt. £1. 1s. Od.; Vol. x1x. £1. 5s. Od. ;
Vol. xx. £1. 10s. Od. : Vol. xx. No. 1, 3/-; No. 2, 4/-; Nos. 3 Sad
4, 1/63 Nos. 5 and 6, 8/-; No.7, rs ; No. 8, 8/-; No. 9, “ioe
Nb, 10, 1/6:
4, Complete sets of the Proceedings, AMeues I.—XIV., ee
may also be obtained on ape to the Seeretaries of? the
Society. : 5;
5, Letters and Communications & the Society should be ee
| addressed to one of the Secretaries, ;
Mr AE, SHIPLEY, Christ’s College. Violeta
Dr E. W. Barnes, Trinity College. [Mathematical.]
Mr A. Woon, Emmanuel College. ‘{Physical.]
6. Presents _ for the coe of the Soviety should be ae os
doer to <S
The Philosophical Labr ary,
: New Museums,
Cambridge.
7, Authors of papers are informed that the Ilastrasion nd Bean.
Diagrams are executed as far as possible by photographic “process” _
work, so drawings should be on a lar ge scale and on: emootl white Se
Bristol ‘board in Indian ink. -
8. Members of the Suciety 7 are requested to. inform the ee
Se TEES of any. change = address.
PROCEEDINGS
OF THE
Cambridge Dhilosophical Society.
On the Oscillations of Superposed Fluids. By H.J. PRIESTLEY,
M.A. [Communicated by W. Welsh, M.A.]
[Recewed 28 October 1909. ]
[Read 8 November 1909. |
In his classical research “On the Theory of Oscillatory Waves”
Stokes* has shewn that the first order period equation for waves
at the free surface of a liquid is modified when we take into
consideration the third order terms. The present paper is under-
taken with the object of finding the corresponding modification
for waves at the common surface of two fluids; and ascertaining
the effect of the small terms on the stability when the upper
fluid has a stream velocity. It is found that the range of wave
lengths for which oscillations are possible is greater than that
given by the first order equation. When the upper fluid has no
stream velocity the period given by this equation is too long
in the case of propagated waves and too short in the case of
standing waves.
For the propagated waves the method adopted is a modification
of that used by Stokes in his Supplement} to the paper quoted
above. This method is found unsuitable for the standing waves,
and it is necessary to use direct approximations from the ordinary
equations of motion. In each case the origin is taken in the
undisturbed surface, with the axis of y vertically upwards. The
sign given to the velocity potential is that adopted by Professor
Lamb, so that the velocity along the # axis is — a
ax
* Math. and Phys. Papers, Tome t. pp. 197 et seq.
+ Ibid. pp. 317 et seq.
VOL. XV. PT. Iv. 20
298 Mr Priestley, On the Oscillations of Superposed Fluids.
I, PROPAGATED WAVES.
Reducing the problem to one of steady motion by the usual
artifice we express the coordinates of any point in terms of the
velocity potential and stream function by means of the equations
x, + 1, = — (b+ W,)/U, +t “S TAY eT Sia) Een ela)
m=0
for the lower liquid, and
Ly + LYo = — (ho + tWr)/ Uy +6 > Da me ate ZULU nn (2)
m=0
for the upper.
A,, A., A;... ete. B,, B,, B,... etc. are two series of quantities
in caseend ne oiler ae magnitude.
The eimde nome to be satisfied at the common surface are
ye UY — Bn Yoel ee epee eee (3),
and the pressure condition
pr/S1 + 2gpr (y+ Cr) = p2/S2 + 2gp2(Y2+ C2) «+. (4),
where is — (s# =a) =F ( fy,
oy
and OC, and C, are constants.
We have yet to choose our origin for wy and we select the
common surface as the line y=0.
Writing S$ = ¢/U, condition (3) gives
Sa = SF = fh > (Bem ae S Ame =)
0
We proceed to find relations between the A’s and B’s from this
equation.
lst Approximation.
whence Ag= x,
and = 22
We take as the common first approximation to 3, and 3, the
mean of the two exact values which we denote by S.
2nd Approximation.
3-9, =1(B,— A.) + (Ai + B,) sin kS +: (B, — A;) cos SS,
whence
A, = B, = 8 (say)|
»—- 9, = 28 sin kS
So omnes
§,=S3—fsnksS
Mr Priestley, On the Oscillations of Superposed Fluids. 299
ard eS
3, — 9, =2 (By — Ay) + se-#8 sin [Bet — A ek]
+0 [B,e** — A,e*™*),
whence we obtain, by equating coefficients of different harmonic
terms in the imaginary part,
B, — Ay= kB?
Vilesd Fea ye) Gunny... ash aaa (C),
A, =D)
while the real part gives
S=S+ 6sin S$ +4(4,+4+ B,) sin 2k5,
$,=S— Bsin kS —4(A,4+ B,) sin 2k.
[8 may now differ from its former value by a small term of
order k8?.]
Ath Approximation.
§, — 9, = 6 (By — Ay) + ve HUB Sin B+ 3 (Ao +B, sin 2K] [Bg __ A th]
4b Le kB sin kS [B, ea 2k _ A, enks |
+ t[Be?** — A,e**],
Equating coefficients of the different harmonic terms in the
imaginary part we obtain
B,—- A, = kp?
B, — A, =3 Bk (A, + B,)
B, — A,=— kB? araleraic euidee olataion (D).
B; ora A,=—3Bk(A,+ B,)
Pressure Condition.
To determine completely the quantities A and B we require
another set of relations between them. These relations are found
from the pressure equation (4). To use this equation we must
find 1/S in terms of sines and cosines of sealiglies of S and this
we proceed to do.
Value of 1/8;.
dz,
2
i ae (Hl)
Mylene) inlik: Tis
W, =
dw, = di a= hy.
From (1)
U, we = 1b fAehl 4 2A,entlT 7
= —[(1+A, cos k9, + 2hA, cos 2h3, +...)
+1(kA,sin k3,+2kA,sin 2k3, + ...)],
when y, = 0.
Thus S,=U,°[1+2k2mA,, cos mk3, + Pim? Ay?
+ 2h?SmnA,A,y cos(m —n)kS,],
20—2
300 Mr Priestley, On the Oscillations of Superposed Fluids.
the last summation being taken once for each pair of values
m and n,
= U,[1+A?+ 2k {A, cos ky i; ... + 3A, cos 8k9,}
2h? {2.A, A, cos k3,}],
neglecting terms of order higher than ee
Expanding 1/S, by the Binomial Theorem and neglecting
terms of order higher than /°8° we have
1/8, = U2 71 — kA? — 2k {A, cos kS, + 2A, cos 2K9, 7
+ 3A, cos 3k3}}
— 2k2.A, {2.4, cos ky}
+ 442 (A? cos? kS, + 44,A, cos kS, cos 2k9,}
L + 4k°4,8 cos kS, — 848.4,° cos* AI, 4
We pass to the corresponding value of 1/S, by changing the
sign of & and using B coefficients.
Since the origin is in the maketh surface the pressure
equation is satisfied over the line y=0 when there is no wave
motion. This gives
Pi U?+ 29p.C = Po U2 + 29p2C.
Using this condition we obtain the following relations from
the pressure equation. ’
lst Approaimation.
29p: Ay = 2gp.By,
which, with A, = B, (equations A), gives
i= 0,
Bo 0
2nd Approximation.
p, U2 (— 2hA, cos KS) + 29p, (Ay + A, cos kS})
= p.U3 (2hB, cos kS,) + 2gp. (By + B, cos kS,).
Remembering A,=B,, A, =B,=8, (B), and
aH = Sh (A),
this gives A= 6, =0;
and 9 (pi — p2)/k = pi UY + p.Ue,
the ordinary period equation *.
3rd Approaimation.
pi U2 (— 2kA, cos kS, — 4h.A, cos 2k9, — kA? + 44°4,? cos? kS})
+ 29p,[A, +A, cos k3, + A, cos 2k9)]
= p,U2 (2kB, cos kS, + 4hB, cos 2k9, — BY + 44°B? cos? k35)
+ 29p,[B, + B, cos kS, + B, cos 2kN.].
* Lamb, Hydrodynamics, § 224, ed. 1895.
ue
Mr Priestley, On the Oscillations of Superposed Fluids. 301
Expressing the harmonic terms in terms of $ instead of 3, and
%., and neglecting terms of order k’8* we obtain, by equating
coefficients of different harmonic terms to zero,
2 (pA, = p2By) ==> (p; =P P2) kB,
gy (pi — p2)/k= p,Uy + p,U?=K, (say),
pi U,? [3h°8? — 4h.A,| + 2gp,[4.—4Fh8"]
= p,U? [(3/°B? + 4kB,] + 29p.(B.+4kP?].
These equations, combined with (C) above, give
A, = — thp? |
Bp a kp? oascenssceencvesesses (E).
A,=kB? p, U7? /K
B, = — kf? oe
We note that, as in the case of waves on a free surface, the
period equation is not changed at this stage of the approximation.
4th Approximation.
In proceeding to the next approximation we adopt the same
method as before. The period equation is obtained from the
coefficient of cosk3 in the reduced pressure condition. This
coefficient gives
piU,?[— 2kA, —$h°B (A,+ B,) +4h*f?|
+ 29p,[A,+4kB (A,+ B,) — 4178? + kB Az]
= p.U?[2khB, —4h°B (A, + B,) —thB?]
+ 29p2[B, — £hB (A. + B.) — 4° — kBB.].
Remembering that
gk (pi = P2) = piU? aE p2U?
to the order k8 and
B,— A,= g Bk (A, ah B,) = 31°88 (pi U7 — P2 U2") /|(p, U, + P2 UY),
we obtain for the period equation
gi (pi— p2) — K = — kB? (pi? Us + p2?U;')/(p, U2 + p2U,?) ...(5).
Before discussing this result we proceed to find the wave
profile. To do this we require the values of the A’s and B’s to
the order k?8*.
The coefficients of the absolute term and cos 2k9 in the
pressure equation are the same as the corresponding coefficients
in the third approximation. Hence A,, B,, A., B, have values
already given (E).
A, and B, are found from the coefficient of cos 3k%, which,
with the help of (D), gives
A, = 2 Pi U0? (2p, U2 — Pe UZ) LOGE,
B, = } p,U? (2p,U2 — p,U7) KB.
302 Mr Priestley, On the Oscillations of Superposed Fluids.
Equation (1) gives us the transcendental equation of the free
surface in the form
x=—%, —A, sinkS, — A,sin 2kS, — Agsin 3/9,,
y = A, + A, cos KS, + A, cos 2k9, + A; cos 3k9,.
From these we find
3, =—2+4+A,sin kx + (A, — $44,") sin 2ka,
and, using values of coefficients already found,
y =[A, + 8B (49, 02K —1)] cos ke
+ 3k8? (p, U2 — p.U2) K cos 2he
+ 8°88 (1 — 6p, U3. p,U2. K-) cos 3ka.
Writing 0 for the amplitude of the principal harmonic term
we have, to order /°6°,
y = bcos ka + $kb? (p, UP — p.U2) K cos 2ka
+ 8k0' [1 — 6p, U,?. p,U.?. K-*] cos 3ka ...... (6).
Both this equation of the wave profile and the period equation
reduce to Stokes’ equations for waves on a free surface on putting
po= 9. :
In discussing these results we shall denote the wave velocity
by c and the stream velocity of the upper fluid by w, so that
U,=-c; U,=u-e.
Writing the period equation in the form
qe: (pr Ge P2) = K= a eB [xk a 2p, U? . Pe U2 . BAY
and remembering that K may be put equal to gk (p, — ps) in the
small terms, we notice that, corresponding to a given wave length,
the small terms have their greatest importance when U,=0 or
c=u and their least importance when p,U;= p.U3.
The first case gives
c= gk (1—s)[1+6"], where s= p/p.
Turning to the equation of the wave profile we see that the
small terms have their greatest importance for this value of ¢.
The equation takes the form
y =beoskx + kb? cos 2kx + 8k°)' cos 3ka,
which is the form Stokes found for waves on a free surface. The
expression for the velocity only differs from Stokes’ free surface
velocity by the factor (1 —s).
The second case gives
20 =K,
whence C= tok (1 —'s) Gee) 4. nee Ge):
and w=+c(1+ s2)/s* bo cea tan a (8).
Mr Priestley, On the Oscillations of Superposed Fluids. 303
For this case the correction to the wave profile has its least
value. (Note. The correction in the cos 3ke term has not its
numerically smallest value.) The wave form is given by
y = b cos ka — 3, hb’ cos 3ke.
[This wave is traced for the value kb =°5.]
Thus waves travelling with velocity given by (7) are least
affected by the small terms. The corresponding stream velocities
in the upper liquid are given by (8).
Hirozade
c=[4gk- (1-s)]2.
A, wave form as given by first approximation.
B, wave form corrected for terms of order k?b?,
_ Stability of waves for a given value of u. The period equa-
tion 1s
piU?? + p,U?2= gk (pi — po) + kB? (pi OY + Pa U, 2')/ (ps U?+ P2 U,?).
In the small term we can take the first order values of c and
hence that term may be considered a known function of k and u.
The period equation therefore gives as a quadratic equation for c
C* (pi + pe) — 2cup,+ psu? = gk (p, — p.) + Pk?6?,
where P=(p?2U¥ + p2U,!)/(p, 02 + p2U?),
304 Mr Priestley, On the Oscillations of Superposed Flucds.
whence
= Ups/ (er + ps)
[gk (es — pa)i(or + pa) + PEE wpips|(pr + pa
Thus ¢ is real if
gk (1 — s)/((1 +s) > ws/(1 + sP — PRB.
Hence the range of unstable wave lengths is smaller than that
given by the first order equation and the corrections for small
terms tend to make the system more stable.
As in the first order case the shortest possible wave travels
with a velocity ws/(1 + 8).
II. STANDING WAVES.
The method of the first part of the paper is unsuitable for the
discussion of standing waves so we proceed as follows:
With the origin in the common surface and the y axis vertically
upwards we assume for the lower liquid
dy tu wr, = > Ajy en ink (ety) |
and for the upper
ds fis wr, = > B eumk (a-tuy) |
The condition to be satisfied at the common surface is
h pid — JPY — & PQ’ = Pahs — Jpry — 4 pgs — FO),
where
q2= Bim Asem + Ww SmnAyAnem ky cos (m — n) ka
= k2A,?(1 + 2ky)+ 442A, A, cos ka
(to third power of the amplitude),
and F'(é) is a function of the time.
This condition gives the equation of the common surface
which we will write
ed.
The condition that no part of either liquid shall flow across the
\2 |
common surface leads to the equations
ae 2b cad =P 0) coe 0
iL tance oe yy tk :
dU i ‘3 dU if ‘ dU At 0 eeceecereeeeeereee eee ( \
dt Ce i (LNG
where (2, 2), (te, V2) are the # and y components of the velocities
in the two liquids.
We proceed to find the values of the A’s and B’s by successive
approximations from the conditions (1).
Mr Priestley, On the Oscillations of Superposed Fluids. 305
1st Approximation.
The equation of the free surface is
9 (pi — po) ¥ = (pi Ai — p2B,) cos ka + F(t).
The origin being taken in the undisturbed surface, we have
F (¢)=0 and :
9 (Pi — P2) Y¥ =(prAi — p2-B,) cos ke.
The surface conditions give
pid, = p2B, +9 (p: a P2) kA,=0,
piAy = p2By reg (p1 — Po) kB, = 0,
whence A, = — B, = pBk" sin pt, (say),
and p?=gk(1—s)/(1+8), where s = p,/p,.
Using the values of A, and B,, we have, as equation of the
surface
y = 8 cos pt cos ka.
2nd Approximation.
The equation of the free surface is
g (pr — po) ¥ =p Ay (1 + hey) cos ka — p2B, (1 —ky) cos ka
= p Az cos 2ha — p2By cos 2ka
—3pl’Ay + tpk°B? + F(t);
whence, using first approximations to A,, B, and y in the small
terms
J (Pir- px) Y= (pA, =o p»B,) cos ka + (p: As = p2Bu) cos 2kax
+ (p; — po) p?8? cos? pt cos? ka
— 4 (pi— ps) p°R? sin? pt + F(Z).
The velocities, required for the surface conditions, are given by
Uy, = — Obs =kA,sin kx, (to first order),
W=— 2 =—kA,coska(1+ ky) —2kA, cos 2ka
=— kA, coskx —2kA,cos 2ka
— pkB? sin pt cos pt cos*kx, (to second order),
with similar values of wu, and 1.
The surface conditions give
(p, A; - p2B;) cos ka + (p, vee p> Be) cos 2ka
— (Pp; — Po) p*R? sin 2pt cos? ka
— 4(p,— pz) p*P? sin 2pt + F(t)
— (p; + po) p*8? sin? ka sin pt cos pt
+ 9 (pi — po) [kA cos ka + 2A, cos 2ha
+ kp§* cos kx cos pt sin pt] = 0,
with a similar equation from the other liquid.
306 Mr Priestley, On the Oscillations of Superposed Fluids.
Equating the coefficients of the absolute term, cos kx and
cos 2ka to zero in these two equations, we have the following sets
of relations :
FE’ ©) = (px p.) gr G2em2pt = 0 2...-.5.3- 252 eee (2),
(from both equations),
prAi— pB, + 9 (pr — pr) RAy = ot eee... (3)
pr 4a — ps Bi — 9 (pi — po) kB, = 0
pr A, — pr By + 2p? (p+ ps) As = — pop®? sin a (4)
Pits — poB,— 2p? (p1-+ Po) B,= pip?8? sin 2pt)
(on making use of the period equation to eliminate q).
From (8) we see that A, is still equal to — B,; we shall still
give them the value p@ksin pt. The period equation will be the
same as before.
From (4) A,=— $po/(p. + ps) pB? sin 2pt,
B, = — $,/(e1 + po) pB? sin 2pt,
and from (2)
F(t) = —4(p: — po) p?8? cos 2pt + C,
where C is a constant of integration.
To keep the origin in the undisturbed surface we take C=0.
The equation of the surface takes the form
y = 8 cos pt cos ka + 4k8? (1 — s)/(1 +s) cos? pt cos 2kza.
3rd Approximation.
9 (Pi — po) ¥ = Prda (1 + hy + Zh?y’) cos ke
— p.B, (1 —ky + thy’) cos ka
+ 0 Ae (1 + 2ky) cos 2ka
— p2Ba (1 — 2ky) cos 2ka
“+ Ge - p2Bs) cos 3ka
—4p,k?[A2(1 + 2ky) + 44, A, cos ka]
+1p.k? [B? (1 — 2ky) + 4B, B, cos ka]
+ F(t).
On using above values for y, A’s and B’s in the small terms
and writing
x (t) = FO) + 4 (pi — pz) p°B? cos 2pt,
this becomes : ti
9 (pi — px) Y¥ = x(t) + C08 kar [pr Ay — p:B,j + cos 2ha [p, A, — p,B]
+ cos 3ka [p, As — p2B;] +4 (1 — po) p?8? cos 2ka cos? pt
24 :
+ gis kp?B*/(p1 + pa) cos pale + 18ps 6pips) cos Spt
( + (7p. + Tp.” — 10p,p2) cos pt
((8p.2 + 8p, — 34,p; ps) cos 3pt ;
+ ii She + (9p.2 + 9p — 38p,p2) cos pt
»
Mr Priestley, On the Oscillations of Superposed Fluids. 307
To apply surface conditions (1) we shall require the
u-velocities to the second order and the v-velocities to the third
order.
These are given by
uy = — 9 = A, sin ho (1 + key) + 2A, sin Bhar
=kA,sin ka + 2kA,sin 2he
+ kp8? sin ka cos ka sin pt cos pt,
7 — a =—kA, coska(1 + ky + thy’)
— 2kA, cos 2kx (1 + 2ky)
— 3kA, cos 3ka
=—kA,coska —2kA, cos 2ka — 3kA, cos 3kax
— pk? sin pt cos pt cos* kx
— £pk?B?/(p, + ps) . cos? pt sin pt [(5p, — 15p,) cos ka
+ (8p: — 17p.) cos 3ka],
with similar values for u, and 2.
Writing these values in the surface conditions (1), using
known approximations to coefficients wherever possible and
eliminating g by means of the period equation in all terms
except those of the first order, we obtain the following sets of
relations :
x () a0) pete teeeeceeeeeceeeeercesenenes gooose scdcoesapocoocconnee (5),
pid; — pr By + 9 (pi — pr) KAy
- (40p,? + 44p.? — 132, p2) sin 3pt
a= Jl 3 (23
sx hp RB’ |(pi + Pp») + (8p:2 + 129.2 — 4p, p.) sin pt |’
piAy a p2B, ctf (p1 oe Po) kB,
(440.7 + 40p.? — 132, p2) sin 3pt
= il hp BeB
Johpi6'|(e. + p)| + (12p,? + 8p,” — 4p; p2) sin pt
Ms i Fi, «Ol ae aes (6),
pits as po Bs + 2p? (pi + p2) As = — pop*B? sin a (7)
piAls — p2B:,— 2p" (pi + p2) Br= pip’ Sin pe) ee
pr A; — prB; + 3p? (pi + p2) As
‘ 7 (21p, — 9p.) sin 3pt
= — 1kp*'p,/(p, + pd) + (5p, — 9p.) sin pe |’
pid; i p.B, — 3p? (pi a P2) B;
21p. — 9p,) sin 3pt
=— tkp’B*p,/(p1 + 2) Be (Bp. se 8
308 Mr Priestley, On the Oscillations of Superposed Fluids.
(5) and (7) shew that F(é), A., B, are not changed by this
closer approximation.
If we write
A,= pk "sn pt+Q,
B, = — pk sin pt — D,,
we obtain, from (6),
C, — D,=— tpkB (p: — po)/(p1 + pz) - (sin pt + sin 3pt).
The part of C, and D, depending on sin pt is indeterminate as
any addition to that part simply means a change in the amplitude
of the principal oscillation.
We take
C, = £pkB*p,/(pi + p2) . sin pt + C, sin 8pt,
D,=$pk*p,/(e: + pz). sin pt + D, sin 3pt.
If we use these values in the two equations (6) and equate the
coefficients of sin pt and sin 3pt to zero we have four equations.
Two of these are the same and lead to the new period equation,
p =gk (1—s)/(1 + s).[1 — 348? (1 + 5)/(1 + 5)}] ....-.(9),
the other two give equations for C, and D,, the solutions of
which are
C, = — sy pkB? (5p + ps’ — 12p,p2)/(p, + ps)” - Sin Spt,
Dy, = — 35 pkB? (p:? + 5p. — 12p,p.)/(p, + po)? Sin 3pt.
Equations (8) give
A, /pkB? = $ p2(3p2— p:)/(pi + pe) sin 3pt
+ 75 P2 (9P2 — 5p1)/(ps + pe)? sin pe,
B;/pkB* = — $p1 (3p: — P2)/(p1 + po)” Sin 3pt
— Zep (9p: — 5p2)/(pr + pe)? sin po.
If we now denote the amplitude of the principal oscillation
by b we find for the equation of the wave profile
y = [bcos pt — 84°05 (p3 + p.*)/(p: + ps)®. cos 3pt] cos ka
kb?
1 oe (1 — p2)/(pi + p2) cos? pt cos 2ka
+ £k70? (p, — 3p2) (8p: — p2)/(pi + po)? cos? pt cos 3ka ...(10).
COMPARISON WITH PROPAGATED WAVE.
Wave Profile.
Putting w=0 im equation (6) of section I we obtain, as the
equation of the profile of the propagated wave when the upper
liquid has no stream velocity
y = beos ka + £kb? (p, — ps)/(p: + pz). cos 2kw
+ 32°03 (p22 + po? — 4p; p2)/(p: + po)’ cos 8ka.
Rn
Mr Priestley, On the Oscillations of Superposed Fluids. 309
Comparing this with the standing wave given by (10) [section IT]
we see that the forms of the propagated and standing waves
are the same if we neglect the second power of the ratio of the
amplitude to the wave length but are different if we proceed to
a higher approximation.
Period.
We have seen that the period equations are not altered by
terms of order &8. When we proceed to the next approximation
the period of the standing wave is given by (9) [section IT] while
that of the propagated wave is found from
p= gh (1 —s)/(1+s)[1 + #6°(1 +s°)/(1 +5)
[(5) section I].
We see that the period 277/p given by the first order equation
is too long for the propagated waves and too short for the standing
ones. We proceed to tabulate the periods for waves of length
10 ft. and 100 ft. We take
kB ="5 and g = 32:16 fis.s.
10 feet 100 feet
Ist order |Propagated| Standing || Ist order |Propagated| Standing
sec, sec. sec. sec. sec. Sec.
die 13:04 14:12 43°98 41°23 44°67
6-093 5-711 6-188 LOA 18:06 19:57
4-193 3°927 4-260 13°26 12°42 13°92
2-796 2-610 2°842 8840 8794 8987
2°135 IESE 2°175 6°752 6°253 6°877
eq: 1557 1-751 5414 4-925 5536
1-398 1:223 1-441 4°42) - 3°868 4:558
1 A SR nate Le ec WR eee ale ct Ce ed
SCHKRADDS
310 Mr Campbell, Discontinwties in Light Emission.
Discontinuities in Lnght Emission. By NoRMAN CAMPBELL,
M.A., Trinity College.
[Read 8 November 1909. ]
SUMMARY.
1. Introduction.
2. ‘The ideas underlying the experiments.
3, 4. The theory of the method of experiment.
5. General nature of the experiments.
6—10. Mathematical theory of the interpretation of the observations.
11—15. The apparatus:
11. The source of light.
12. The photo-electric cells.
13. The measuring instruments.
14. The high resistance. :
15. Measurement of the instrumental constants.
16. Numerical calculations showing the possibility of the experiment.
17. Combination of the observations.
18—20. The experimental difficulties which have prevented the at-
tainment of results.
§1. The following pages are the account of an experiment
which failed. The occasional publication of a description of such
failures may be justified by two reasons, both of which appear to
me sufficient in the present case. In the first place, the theory of
the experiment may be of interest: and, according to the view
which is taken of the causes of failure, others better equipped for
the task may be induced to repeat the attempt, or others, to whom
the same idea may occur, may be saved from wasting their time.
In the second place, the methods of experiment, if they are novel,
though unsuccessful in their immediate object, may have other
applications.
§ 2. The ideas on which the experiment was based are not
easy to describe in a brief title: a little explanation is needed.
According to all modern theories of radiation, the emission of
light is discontinuous in time. Whatever may be the nature of
the radiators from which the light proceeds, there is little doubt
that their vibration is not continuous. They are set into vibration
by some external disturbance, such as the impact of electrons, and
continue vibrating until the energy so acquired is dissipated by
the damping due to radiation: they are then quiescent until the
occurrence of a fresh disturbance.
But there are at least two theories of radiation which suggest
that light emission is discontinuous in space as well as in time.
o
Mr Campbell, Discontinwmities in Light Emission. 311
These theories were proposed by J. J. Thomson* and by Planck‘.
They both suggest (at least if we interpret Planck’s theory in the
sense given to 1t by Stark}) that the light from a single radiator
is not emitted equally in all directions, but is concentrated along
a finite number of narrow tubes radiating from the radiator: they
also suggest that the energy emitted by such a radiator in virtue
of a single disturbance is not infinitely divisible, but only divisible
into a finite number of equal parcels, the magnitude of which,
according to Planck, depends on the frequency : further, this finite
number is usually quite small under experimental conditions.
This view is capable of explaining many difficulties connected
with the ionisation of gases and allied phenomena which are
quite incomprehensible on the older theory that the light spreads
out from the radiator as a spherical wave. But it also raises some
new difficulties in connection with optical interference. If the
light from a single radiator can only be split into a small number
of parts, then, if the beam of light from an ordinary source, con-
taining a great number of separate radiators, is divided by any of
the ordinary interference methods, the light in one beam must, in
general, come from radiators different from those which emit the
light in the other. Two rays of light which come from different
radiators will be termed ‘independent.’
And here a distinction, which may be of importance for our
purpose, must be made between the two methods of exciting inter-
ference. In the first method, of which Fresnel’s mirrors are
typical, the two beams which are made to interfere eventually
are emitted at different angles from the source: they will be
independent, in our present sense, if it be true that the light
from a single radiator is emitted in one direction only, and
this conclusion requires no assumptions as to the divisibility of
the energy in the light from a single radiator. In the second
method, exemplified by Michelson’s interferometer, the two beams
proceed from the source in the same direction. They will be
independent, only if it is impossible to split up the energy from a
single radiator into two parts, so that the beam reflected by the
half-silvered mirror must come from different radiators from that
transmitted by it. On Planck’s theory of radiation there should
be no distinction important for our purpose between the two
interference methods, but on Thomson’s theory it is possible that
the two beams produced by the second method are dependent,
while those produced by the first are independent.
Now it is not difficult to imagine why two independent beams
* See Electricity and Matter, London, 1904, p. 63, or Proc. Camb. Phil. Soc. xtv.
1907, p. 417.
+ M. Planck, Wdarmestrahlung, Leipzig, 1906.
¥ J. Stark, Phys. Zeit. x. 1909, p. 579.
312 Mr Campbell, Discontinuities in Light Emission.
should show interference, but it is difficult to explain why two
beams should interfere when they come originally from a ‘single
source, and should not interfere when they come originally from
‘different sources. For, on this view, in both cases they really
come from different radiators. Accordingly it appeared that con-
siderable value would attach to any experiment which should
indicate, by means of observations other than those of optical
interference, whether the two beams, into which a beam from a
single source of light is divided by interference methods, are to be
regarded as coming from the same or from different radiators.
§3. Now the theory recently given by Schweidler*, and applied
to radioactive processes by Kohlrausch+, by Meyer and Regenerf?,
and by Geiger§, provides a very powerful method of investigating
any discontinuous process. Schweidler showed that if any effect,
of which the magnitude can be measured, is due to the random
occurrence of a finite number of independent events, then the
magnitude of the effect will not be constant, but will show fluctua-
tions about a mean value, and that from the magnitude of the
fluctuations the number of independent events can be calculated.
Further, if the magnitude of the sum or difference of two effects
so constituted is measured, the square of the mean fluctuation of
the sum or difference is the sum of the squares of the mean
fluctuations of the two effects, if, and only if, the events which
constitute one event are wholly independent of those which
constitute the other. If, on the other hand, there is complete
correlation between the events constituting the two effects, the
mean fluctuation of the difference will be zero. In a recent
paper||, which will be quoted frequently below, I have en-
deavoured to investigate closely the application of this theory to
experiment.
§ 4. Suppose, then, that by some means we can measure the
intensity of a beam of light in such a way that the total intensity is
the sum of the intensities of the radiations from the isolated radia-
tors of which the source is composed. Let us split up the beam from
a ‘single source’ by one of the ordinary interference methods and
measure in this way the difference in the intensity of the resulting
beams, adjusting the arrangements so that the mean difference is
zero. If the older theory of radiation is correct, there is complete
correlation between the ‘events’ which constitute the two beams:
when a radiator sends light into one beam, it also sends it into
the other. But if the newer theory of the radiation is correct,
* Schweidler, Congrés Internat. a Liége, 1904.
+ Kohlrausch, Wien. Ber. 1906, p. 673.
+ Meyer and Regener, An. Ph. xxv. p. 757.
§ Geiger, Phil. Mag. April 1908, p. 539.
|| Campbell, Proc. Camb. Phil. Soc. xv. 1909, p. 117.
Mr Campbell, Discontinuities in Light Emission. 313
the ‘events’ are independent, or very nearly so, for in general each
radiator sends its radiation into one beam and not into both. On
the first theory the mean fluctuation of the difference should be
zero: on the second the square of the mean fluctuation should
be the sum of the squares of the fluctuations of either beam
separately.
§5. The application of these ideas to experiment was
attempted in the following way. The intensity of the beams
was measured by means of the photo-electric current which they
excite in the alloy of sodium and potassium in a high vacuum.
It seems reasonable at the outset to suppose that each train of
radiation emitted by a single radiator, when it falls on the alloy,
liberates a number of electrons which is, on the average, the same
for all radiators and independent of the total intensity of the
beam, i.e. the number of such trains emitted in a given time. If
this assumption be true, then the difference between the photo-
electric currents due to the two beams will be a function of the
difference in the number of trains of radiation constituting the
two beams, and measurements of the fluctuations of this difference
will enable information to be deduced as to the independence of
these trains. The fluctuations were measured by Meyer and
Regener’s method of observing the readings of an electrometer,
the quadrants of which were connected to the two ends of a high
resistance through which the current passed.
§6. Before proceeding to detail the experimental methods it
will be well to consider the theory a little more closely: if this
order had been adopted in the first instance much time would
have been saved.
The main result of the previous paper* may be stated as
follows. Let X7 be the average number of events which happen
in a small time 7, and let x be the deviation of that number
from its mean value during the time 7: let
represent the motion of the indicator of the measuring instrument
at all times ¢ subsequent to the happening of one of the events,
and @,” the square of the mean deviation of the indicator from
its mean position for all times 7’ from the moment of starting the
observations, where 7’ is a time long’ compared with the time
constants of the measuring instrument. Then it is shown that
Tt
Ge il, | WO ere ten (2),
§7. We have first to calculate a, The ‘events’ in our case
are the liberation of individual electrons. Our fundamental
* Campbell, loc. cit.
VOL. XV. PT. IV. 21
314 Mr Campbell, Discontinwities in Light Emission.
assumption states that the number of electrons liberated is pro-
portional (at any rate for a given intensity of the light) to the
number of light disturbances falling on the cell. If N is the
average number of such disturbances striking the cell in unit
time, w the average number of electrons liberated by each light
disturbance, then
XT SNOT 2.0 one Ce (3).
The fluctuations of X, which are measured by 2? arise (1) from
fluctuations of NV and (2) from fluctuations in w. The introduc-
tion of » allows for all changes of the absorption of the light in
different parts of the optical train, and for all differences in the
state of the cell and the manner of the incidence of the light
upon it. Then, if € and 7 are the deviations of Nv and o respec-
tively from their mean values during any very short time 7, we have
(Xr + 2) =(Nrt €)(@ 44) ceececerecesees (4),
and ei Nernst ee + Estas: ae eeane eee (5),
and a? =[N272n? + Ew? + £2? + 2NrnEo + 2Nrrré + 267] ...(6).
It will be assumed that & and 7 are wholly independent, hence
né, n?& and £n? are all zero, since 7 and & are zero. Also, since
z tends to the limit zero, N?7? is infinitesimal compared to o.
Therefore = E(w 9?) estas sade eee eee (i):
As was proved in the previous paper,
BaNr fo eee (8).
Hence = N(@? ait oo ee (9).
§ 8. (9) gives the result when we are considering a single
beam falling on a single cell and measuring the fluctuations of
that cell as Meyer and Regener* measured the fluctuations of a
single source of a rays. Let us now consider a second cell (the
quantities referring to which are distinguished by dashes) and
measure the fluctuations in the quantity X — X’, where X =X’.
In this case 7 and 7’ are independent and it will be assumed that
n=; & and &’ are dependent or independent according as the
two beams of light are dependent or independent in the sense
which has been discussed. Then it is easy to show that, if «
now represents the fluctuations in (X — X’)7,
Bf = QIN (@? ite ae ee (10)
if the beams are independent, or”
Bm DN GF Tee csadiesiscesh ee (10’)
if the beams are dependent.
* Meyer and Regener, loc. cit.
Mr Campbell, Discontinuities in Light Emission. 315
§9. We cannot estimate the value of 7? until we know (and
we are not likely to know in the near future) the causes of the
fluctuations of w. But, from the general theory of probability, it
a) ‘
is certain that ie will diminish as w increases. Further the same
@
quantity will, almost certainly, diminish as the number of electrons
which come under the influence of the light beam increases: for
w fluctuates because all those electrons are not in the same con-
dition, and in a very large collection of electrons the distribution
of electrons of different properties is likely to be very nearly the
same. Accordingly, on the older theory of light, we should expect
T to be very small: for any light disturbance is spread over the
wo?
whole surface of the cell and of the optical train, and acts upon a
vast number of electrons. But, on the theories of light which
form the basis of this experiment, the area of the surface affected
by any one light disturbance is very small and the number of
electrons in that surface may possibly be as small as one. With
these considerations in mind, let us consider how observations of
the fluctuation of the measuring instrument might be applied to
test the rival theories. (It must be remembered that, in any
comparable series of experiments, f(t) will be the same, so that
O07? is proportional to 2/7.)
In the first place we might compare the fluctuations of X — X’,
Le. the fluctuations of the balanced cells, (1) when we know that
the two beams are independent and (2) in the case in which we
wish to discover if they are independent. The ratio of the
fluctuations in (1) to those in (2) should be 1 if the beams in
or +
2
if they are dependent. If 7?
(2) are independent, and
were the same in both cases and
§,|5.!
; were large compared to 1,
the two ratios might well be indistinguishable: it is for this
2
reason important to note that om is certainly not likely to be
@
large on the ‘spherical wave’ theory of light. If that theory be
true we should expect the ratio in case (2) to be much greater
than that in case (1); 1f the ‘bundle of energy’ theory be true
we should expect the two ratios to be equal. The objection to
this method of test is that it is difficult to ensure that the optical
trains and the entire apparatus remain the same, when the change
is made from the beams known to be independent (probably two
different lamps) to the beams which it is desired to test.
In the second place, we may compare the fluctuations of
21—2
316 Mr Campbell, Discontinuities in LInght Emission.
A — X’, with those of X or of X’, by simply putting one of the
two beams investigated out of action. If the two beams are
independent the ratio of the fluctuations in the first case to those
in the second should be 2, if they are dependent it should be
2 =
ae, Here again a distinction will be possible only if 7? for
wo’ +7
the dependent beams is small compared to w% The objection
to this method is that, as will be seen, it is not easy to exclude
sources of fluctuation which affect the single cell, but do not affect
the balanced cells.
= .
§ 10. Let us now investigate briefly the quantity | Ff? (é) dt.
0
It can be shown by mere algebra that, if the form of f(t) given
in equation (2) of the previous paper is correct, involving the
constancy of the capacity of the system and the proportionality
of f(t) to the charge communicated to the instrument, we have
ae _ es? a8(pt+atB)
ip MOL eat era rrceaa Te wee es
as ee (p + 2a) (a? + b?)
OC?" dap (p + a2 + 8)
according as a and 8 are real or imaginary*. Here e is the
charge on an electron, C the capacity of the system, & the re-
sistance between the quadrants of the electrometer, p=1/RC the
logarithmic constant of decay of the charge, a and 8, or a and 8,
time constants determined by the period and damping of the
electrometer, and s the sensitiveness of that instrument, ie. the
ratio of the deflection to the steady P.D. between the quadrants.
The following deductions from (11) and (11’) are important, if
it is desired to make 07° as large as possible:
(1) It is desirable to decrease C as far as possible : but, taking
into account the fact that p is a function of C and (4) below, C
practically enters only as the first power and not as the square.
(2) s should be made as large as possible. Since s enters as
its square its value is far more important than that of C.
(3) & should be made as large as possible. It will be seen
that there are practical limits to the value of R.
(4) So long as p is small compared with a and £8, or a and b,
which are of the same order of magnitude in all ordinary instru-
* Tt should be remarked that the previous paper is deficient in its algebra. It
was not noticed that equation (20) can be reduced to the form given here and, con-
sequently, the conclusions of paragraph 10 as to the most desirable values of the
instrumental constants are worthless. The conclusions given here are believed to
be correct, subject to further considerations given below in paragraph 15.
Mr Campbell, Discontinuities in Light Emission. 317
ments, the value of a, @, a, b is of little importance. If a=b and
a/p is changed from infinity to 1, the value of @7” is only decreased
in the ratio 5 to 3.
This conclusion may be surprising till it is remembered
that /(¢) represents the motion of the needle after a sudden
disturbance. The values of the time constants of the instru-
ment, supposed smaller than that of the high resistance, affect
only the initial part of the motion.
Accordingly it is clear so far that the sensitiveness of the
instrument is the one thing that really matters. A Dolezalek
electrometer will be much preferable to any form of electroscope
with smaller capacity but smaller sensitiveness; for the capacity
of the system apart from the electrometer will not be insignificant
compared with that of the electrometer.
The actual experimental arrangements will now be described.
Although no results have been obtained as yet, I think that, in
all essentials, they have attained a final form. But since no results
are claimed.as yet, a very detailed account will not be necessary.
In all quantitative statements that follow, electrostatic units
are employed.
§11. In the earlier experiments the source of light was a
Nernst lamp of 50 watts heated by the town alternating supply
which was the most constant source of current available. To
indicate changes in the intensity of the light a small thermo-
element in a vacuum was placed immediately under the lamp:
changes of 1 in 10,000 could be detected with certainty. Since
the constancy of the light proved insufficient an attempt was
made to use an Osram lamp of 8 volts and 16 watts, but, though
by the use of two such lamps some preliminary observations on
the fluctuations of two independent sources have been made, the
intensity of the light was insufficient for the main experiment.
It is hoped in the near future to be able to run a Nernst lamp of
50 or 100 watts off accumulators of constant potential.
When continuous current was used to excite the lamp, its
constancy was measured by making the filament one arm of a
Wheatstone bridge, for which the exciting battery served as the
source of current. A change of 1 in 10° of the resistance could
be detected, or, since the illumination appears to vary approxi-
mately as the 10th power of the resistance, a change of 1 in 10*
of the illumination.
The light from the lamp was rendered parallel by a simple
lens of 7:5 cm. focal length and 4°5 cm. aperture. The resulting
beam was split into two parts, either by interposing in its path a
half-silvered mirror, or two full mirrors, one behind the other, of
which the front mirror had a sharp edge; the plane of the mirrors
318 Mr Campbell, Discontimuties in Light Emission.
made an angle of approximately 45° with the direction of the light.
The resulting two beams were suitably reflected by mirrors and
brought to a focus on the surface of the alloy in the photo-electric
cells by lenses similar to that previously mentioned. The angle of
incidence of the light on the surface of the alloy was approxi-
mately 65°.
In order to adjust the currents through the two photo-electric
cells to equality, a shutter moved by a fine screw was inserted in
front of one of the cells. The light acting on the cells in the
absence of the shutter was first adjusted as closely as possible to
give equal currents, and the final adjustment made by means of
The figure shows only one cell; the
second cell was exactly similar and
lay beneath the plane of the paper.
tube leading to
Second cell
Cu plate
Alloy K-Na
Scale of Cms.
a eae
Fig. 1.
the shutter. The primary adjustment was made by varying the
distance of the lamps from the cells, when two independent lamps
were used: by moving the front mirror across the path of the
beam, when the light from a single lamp was split by two full
mirrors: and by altering the inclination of the half-silvered mirror
to the path of the light, when the splitting was effected by the
half-silvered mirror.
§ 12. As photo-electric cells an attempt was first made to use
Mr Campbell, Discontinwities in Light Emassion. 319
rubidium cells made by the Polyphos Elek. Ges. of Munich: but,
though these were more sensitive than any made subsequently,
the differences between various cells were too great to permit of
their use. It should be noted that these cells, unlike those made
usually by the firm, were exhausted to the highest possible
vacuum. It is necessary in these experiments to avoid the
presence of any gas in the cells which might give rise to ‘ionisa-
tion by collision, for two reasons. (1) If there is ionisation by
collision it is very improbable that the fundamental assumption
of the theory given above, that the current through the cells is
simply proportional to the number of light disturbances incident
upon it, is fulfilled. (2) As was pointed out in the previous
paper *, if the current is not saturated, the effective value R of
the resistance between the quadrants of the electrometer varies
with the intensity of the light: there is a portion of the con-
ductivity which does not depend on the properties of the conductor
inserted specially, the magnitude of which it is almost impossible
to measure, and the constancy of which cannot be assured.
Cells were then made containing the alloy of sodium and
potassium. The form ultimately adopted is shown in fig. 1f.
After the vessel had been evacuated the alloy was sucked into
the bulb A. When the evacuation had been completed it was
allowed to flow into the vessel: B by inclining the structure.
The difficulties which attend the use of the alloy have been
discussed recently so fully by Elster and Geitel{ that little more
need be said. Of the two great difficulties which they found, the
distillation of the alloy on to the other electrode and the con-
tamination of its surface with particles of oxide, the former was
of no importance in this work and the latter of but slight
importance. The presence of oxide would only increase the value
of 7%. But a method was found of getting rid of the small specks
of oxide by a process much simpler than filtering. If, when the
alloy is in its final position, one point at its edge is warmed
‘slightly (the neighbourhood of the hand is sufficient) the change
in the surface tension is sufficient to drive all impurities to the
opposite wall of the cell, leaving a perfectly clean surface. The
warm body must be kept in position while the experiment is in
progress, but the most careful experiments failed to show any
changes in the conductivity of the cells due to its presence.
The cells were exhausted by charcoal immersed in liquid air
before being placed in position. A second tube of charcoal was
always kept in liquid air while observations were in progress.
* Campbell, loc. cit. § 16.
+ The tube joining A and B should have been drawn so that it joins B between
the copper plate and the surface of the alloy.
+ Hlster and Geitel, Phys. Zeit. x. 1909, p. 457.
320 Mr Campbell, Discontinuities in Light Emission.
Fig. 2 gives the relation between the potential difference on one
of the cells and the current through it. It will be seen that very
complete saturation is attained: the point on the curve which is
marked by the cross corresponds to the P.D. actually used in the
observations.
The electrodes of the two photo-electric cells were connected
with the battery of small accumulators, which provided the po-
tential used, in such a way that the currents through them to the
electrometer were opposite in sign. See fig. 3 which shows the
connections of the measuring circuit.
150
Current (£.8.U.)
3
i) 07 0-2 0-3 0-4
P. D. (&.s.0.)
Fig. 2.
§13. The electrometer employed was of the Dolezalek pattern.
The constants a and @ (real for low potentials on the needle, and
imaginary for high potentials) were changed by altering the
potential on the needle. These constants were determined in the
ordinary way by observing the motion of the needle when dis-
placed from its zero position with the quadrants kept at constant
potential. The sensitiveness in most cases was about 10% the
scale being 14 metres distant and capable of readings to } division.
A tilted electroscope was also connected to the common
electrode of the cells. It was more convenient than the electro-
meter for some purposes, such as the measurement of the total
current through either cell. It was for such measurements that
the capacity box (9 x 10° to 9 x 10°) shown in fig. 3 was employed.
Mr Campbell, Discontinuities in Light Emission.
Earth
+ [Eeea le =i
life WN’
re)
P2
{
WwW
Fig. 3.
5
ms
bw
photo-electric cells.
small accumulators,
accumulators for potentiometer circuits P,, P,.
sub-divided capacity box (1 micro-farad).
electrometer.
tilted electroscope.
Xylol-alcohol resistance.
guard-rings,
key insulating electrode system.
Ob ty
Ss
~
Ran
321
$22 Mr Campbell, Discontinwities in Light Emission.
§ 14. The resistance by which the electrometer was shunted
was * of the order of 7b E.8.U. (9 x LO" ohms), Such resistances
are too low to be provided by ionised air in the manner now
associated with the name of Bronson; moreover, such air re-
sistances give rise to fluctuations, due to the finitude of the
number of rays by which the air is ionised, which would be of
the same order of magnitude as those that are here investigated.
Several substances were tried as materials for the required re-
sistance, including graphite, copper oxide, Phillips’ conducting
glass and various Tiquids, The latter eventually proved the most
satisfactory. A mixture of Xylol and Ethyl Alcohol (from 30
to 5 parts of the former to 1 ‘of the latter) was ultimately em-
ployed in a tube of such a form that the distance between the
platinum electrodes could be varied. One end of the resistance
was connected to the common electrode of the cells, the other to
a potentiometer arrangement, the need for which will be explained
later.
The insulation of the electrode system, of sulphur and amber,
was such that its conductivity was certainly less than 0°01 of that
of the artificial resistance: its conductivity is therefore neglected.
The value of R was determined directly by Ohm’s Law. One
of the cells being kept dark, the light falling on the other was
adjusted to such an intensity as to give a “convenient current
through the cell. The magnitude of this current was measured
by the electroscope and capacity box—the electrometer ee
taken out of the circuit, The electrometer was then connecte
again and such a potential applied to the potentiometer P, that
the electrometer showed no deflection. Then the potential between
the ends of the resistance was such that the current through the
resistance was equal to that through the photo-electric cell, In
this manner it could be shown that the resistances used obeyed
Ohm’s Law with an accuracy of 1°/, over a range of P.D. from
15 to 0:002 E.s.u. The polaris ation EME, of the liquid resistance
was certainly less than 10~ E.s.U,
§ 15. The only quantity in equation (11) the measurement of
which presented any difficulty was the capacity. ‘The capacity
of the electrometer was a considerable part of that of the whole
electrode system, and it is well known that this capacity is not
constant, but varies with the deflection and, so far as I can make
out, with the rate of movement of the needle. The most hopeful
way of obtaining an effective value for the capacity of the electrode
system appeared to be by measuring the value of A and of
p=1/RC: p was determined by observing the rate of decay of
the deflection of the electrometer, when the electrode system was
raised to a given potential and then insulated. (The initial part
of the decay was neglected, because of the influence of the time
Mr Campbell, Discontinuities in Light Emission. 323
constants of the electrometer.) If the capacity of the system
varies with the deflection, the resulting curve of deflection against
time ought not to be exponential. As a matter of fact, 1t ap-
peared to be perfectly exponential, but, on the other hand, the
calculated value of the capacity increases regularly with a decrease
in &, On decreasing £ from 0:13 to 0:013 C appeared to increase
from 380 to 500.
That this peculiarity was due to the electrometer was proved
by the fact that, if the electrometer were disconnected and the
decay observed by the electroscope, the capacity being varied by
means of the capacity box, perfectly consistent results were
obtained, A great deal of time was wasted in an inquiry into
this matter and no conclusive information was obtained.. The
matter is not of first class importance, because in comparing
fluctuations, care would, of course, be taken to keep the instru-
mental constants the same: and, in estimating the absolute value
of N (w? + 7), the errors in the measurement of the fluctuations
are likely to be as serious as the uncertainty in the value of
the capacity.
§ 16. It will be well to consider here for a moment whether
the magnitude of the fluctuations to be expected on the theory:
of light which is under discussion is such that it is likely to be
capable of detection and measurement. On Planck’s theory some
estimate of this magnitude can be made.
According to that theory the quantity of energy (e) contained
in one light disturbance is given by
e=6'5 x 10-*’ pv, where v is the frequency of the light.
Hence if we know the amount of energy in each of the electrons
shot off from the photo-electric substance, we can deduce the
average number of electrons shot off by each light disturbance :
ie. the quantity w. The application in this manner of Planck’s
theory to the photo-electric effect has been made by Einstein*
and by Joffét, the latter giving numerical calculations based upon
the work of Ladenburg}. It appears from these calculations that
the energy given by the light to the electrons shot out from zine
is about one-third of that contained in each light disturbance: so
that @ is about 3. For the alloy of sodium and potassium, which
is more photo-electric, is certainly greater. But, since a mini-
mum estimate is desired, we will take w as 1, and will put
n° = 0—though, if w is as small as 1 it is probable that 7? is of
the same order as .
* Kinstein, Ann. d. Phys. xx. 1906, p. 199.
+ Jofté, Ann. d. Phys. xxtv. 1907, p. 939.
{+ Ladenburg, Phys, Zeit. vir. 1907, p. 590.
324 Mr Campbell, Discontinwities in Light Emission.
The total current through either cell (2) is given by
VCO Nu Mats tL (12).
The magnitudes of the various measured instrumental constants
in the experiments which have been made are approximately as
follows :
(These values are not the most favourable that can be obtained
experimentally, so that our estimate is once more a minimum
estimate.)
a=b=02, R=02, C=500, s=10% ¢=100.
T
Assuming that the value of | J? (6) dé can be calculated from
0
(11’), it is found to be about 2 x 10%. Hence for the fluctuations
of the balanced cells illuminated by independent sources
Op? = 2 (w? + 4?) N.2. 108
21 pe
= 4,109.9 =7 ev
= 16,
or al} O72 = 4 (about).
This value is just on the limit of the range within which
detection is possible—it means that the electrometer spot will be
on the average about 4 divisions distant from its mean position.
But this is a minimum estimate: as a matter of fact such pre-
liminary observations as have been made with two independent
sources (two Osram lamps) indicate that, with these values for
the instrumental constants, nl 072 is about 18—which is of the
right order of magnitude.
§17. A brief explanation must be given of the manner in
which the observations were taken and the value of 07? deduced
from them.
This quantity is the arithmetic mean of the squares of the
deviation of the indicator from its mean position for all times
after a period 7’ from the moment that the electrode is insulated.
As was pointed out in the previous paper, the most satisfactory
way of estimating @7? would be by recording the motion of the
spot photographically and integrating the resulting curve (with
the ordinates squared) graphically. But since, at least at
present, no great accuracy has been required, the observations
have been taken by eye at equidistant intervals of time (4”)
indicated by a metronome. 200 such observations constitute one
series, of which the probable error is, as has been shown, 1 |W 200.
Mr Campbell, Discontinuities in Light Emission. 325
In almost all series there was, in addition to the fluctuations,
a slow drift of the spot in one direction or the other. To allow
for this drift, it was assumed to be linear so that
It is easy to see that, if we treat the n observations made as
readings from which the constants u and v are to be determined
by a least square solution, 07? is the mean of the square of the
residuals, so that
7) Sa (26) 12 n—Il 2
07? = 02 parerne os a ee =O, — = (b.0:)¢ .-(14).
Any series in which there appeared to be any suspicion of a
change in the drift was rejected. aes
The arithmetical work in finding 07? was heavy, but with
practice and the aid of a calculating machine a single series could
be solved in 20 minutes.
§18. At the beginning of the work a great deal of time was
wasted because a complete theory of the experiment was not
known. But once the influence of the various instrumental con-
stants upon the fluctuations was discovered, all the experimental
difficulties which had been anticipated were quickly overcome.
They were such as attend all work upon electrostatic currents and
no further reference need be made to them.
Blank experiments, made without the action of the light at
all, showed that, when no light acted, there were no fluctuations
whatever. For two hours or more the spot on the scale would
keep perfectly steady or move constantly with a very slow drift in
one direction. It is certain, therefore, that no trouble need be
expected from such sources as changes in the potential of the
battery used to send the current through the cells.
It was also important to show that the high resistance did not
introduce disturbing fluctuations, such as would certainly have
been introduced by a Bronson air resistance. For this purpose
two similar high resistances were used and opposite potentials
applied to their ends, so that the currents flowing through them
were opposite in direction and equal in magnitude to each other
and to the photo-electric current employed. No fluctuations what-
ever could be detected, though the steady drift of the spot was
greater than in the former case, when practically no current was
flowing through the resistance.
§19. But there were two outstanding difficulties. The first
of these, the difficulty of determining the capacity, has been noted
already. The second was far more serious and has prevented, up
326 Mr Campbell, Discontinuities in Light Emission.
to the present time, any results being obtained. It was found
that the balance of the two currents through the cells was upset,
if the total intensity of the light was changed. Whether the two
currents were excited: by different lamps lit by the same current
or by the hght from a single lamp split into two parts, a change
in the current supplying the lamp or lamps was attended by a
very serious displacement of the balance of the currents.
A great deal of work has been done in the effort to discover
the cause of this defect and to remove it: but it has remained as
mysterious as ever. It was thought at first that the cause must
lie Im some asymmetry of the photo- electric cells*.
That this explanation is not sufficient was shown by focussing
the two beams, not on photo-electric cells, but on thermo-elements.
Though these elements were much less sensitive than the cells,
there was no doubt that the balance of the thermo-elements was
upset in exactly the same way as the balance of the photo-electric
cells by a change in the total illumination. It appears then that
the effect is connected rather with the optical train employed than
with the detectors: and additional evidence for this view was
found in the fact that the sign of the change in the balance could
be changed by comparatively trifling alterations in the mirrors
and lenses. But in no case were attempts to reduce the change
to zero successful.
The magnitude of the change in balance (measured relatively
to the whole current passing through either cell) increases very
rapidly with an increase in the total light. By placing diaphragms
before the lamp and causing a given increase in the illumination
by shunting a constant resistance in the lamp circuit, it was found
that the change in the balance varied approximately as the cube
of the total light.
Tt was thought at one time that the change in the balance
might be due to the fact that there was a portion of the current
passing to the electrode which was independent of the light. It
is easy to see that, if there were such a portion, the balance
between the currents would hold only for one intensity of the
light. The experiments that have just been noted show that
* It was thought at one time that the reason might lie in the fact that the
current through the cells was not strictly proportional to the intensity of the light
acting upon them: and observations were made with the object of testing this
proportionality. The variations in the intensity of the light were produced by
passing it through a photographie lens in which diaphragms of known aperture
could be inserted. It was found that the current was not proportional to the light,
being relatively smaller for smaller intensities of the light. It was discovered sub-
sequently that a similar result for ultra-violet light acting on zinc had previously
been noted by Griffith (Phil. Mag. v1. 14, 1907, p. 297). But the matter is not
very important for our purpose, because all that is necessary, in order that a
change in the total light should not alter the balance, is that the current should
be the same function of the light in the two cells.
Mr Campbell, Discontinuities m Light Emission. 327
such a cause cannot account for the whole of the effect: but it was
found that by introducing a current independent of the light the
magnitude of the effect could be decreased very considerably.
Such a current was introduced by raising the end of the high
resistance R distant from the electrode to a suitable potential,
instead of connecting it to earth and the earthed quadrants of
the electrometer. The magnitude of this potential had to be
found by trial. But though the effect could be reduced greatly
by this device, it could not be entirely abolished. The best state
of affairs that could be produced was when, on changing the total
light, the spot on the scale first moved rapidly a short distance in
one direction and then gradually took up a final position on the
other side of the zero corresponding to the new balance.
§ 20. The change of balance was of especial importance in the
earlier experiments, because the most constant source of potential
which was available for a Nernst lamp was subject to variations of
as much as 5°/,. But at the outset it was not even thought
worth while to make special efforts to obtain a more constant
source, until all possible investigations into the matter had been
made. If there were any uncertainty whether the observed
fluctuations were due to changes in the total intensity of the
light or to changes in the relative intensity of the two beams,
the experiments could be of no possible value. It was only when
all efforts to get rid of the difficulty had failed that it seemed
desirable to proceed further. :
It appeared, then, that errors due to this source could be
detected, if not eliminated, by comparing the fluctuations due to
one of the cells with those due to both of the cells illuminated by
totally independent sources. Changes in the total intensity of
the light, even if they atfect the latter experiment, must be much
more serious in the former. And, if it were found that these
changes were so small that the fluctuations in the former case
were, as theory indicates, half those in the latter, then it would
be certain that the fluctuations were due to changes in the
relative intensity of the two sources and not to changes in the
total intensity of the light.
In order to measure the fluctuations due to one source
separately, the current through the photo-electric cell was
balanced by Meyer and Regener’s method of sending an equal
and opposite current through the high resistance R by applying
to its ends a P.D. by means of the potentiometer. It is not in-
tended in this paper to give any actual results, but it has been
found that the total light from two Osram lamps run from the
same battery in parallel is so constant that the theoretical relation
is fulfilled within the limits of error: the fluctuations of one
328 Mr Campbell, Discontinuities in Inght Emission.
source are certainly less than those of two: and, accordingly, the
main source of the fluctuations must lie in changes in the relative
intensities of the lamps.
It is for this reason that the work that has been done appears
of sufficient promise to justify publication. If results are ulti-
mately obtained, the description of the methods and the narration
of the results would be so lengthy that it appears desirable to
divide thus the account into two parts.
Mr Horton, The emission of positwe rays, ete. 329 .
The emission of positive rays from heated phosphorus compounds.
By Frank Horton, M.A., St John’s College.
[Read 25 October 1909.]
Prof. Sir J. J. Thomson has shown that certain salts when
heated give. rise to a large positive ionisation*. Of the salts he
experimented with the greatest effect was given by phosphates,
and of these aluminium phosphate was found to be the most
active. From this salt at a red heat Sir J. J. Thomson found
that the emission was so great as to be easily measured with a
galvanometer. The following experiments were made with the
object of discovering whether there was any connection between
this phenomenon and the “anode rays” of Gehrcke and Reichen-
heim. These experimenters have found+ that when certain salts
are used as anodes in a vacuum tube they give off positive rays
which proceed at right angles to the surface of the anode and
behave in a manner completely analogous to that of cathode rays.
Fig. 1.
A, anode. Kk, cathode.
These anode rays consist of positively charged particles of atomic
dimensions moving with a velocity of about 10’ cms. per sec.
Spectroscopic evidence has proved them to consist of atoms of
the metal contained in the salt anode. Gehrcke and Reichenheim
found that anode rays were most freely emitted by the halogen
salts of the alkali metals, and they consider that in general the
most suitable salts to use as anodes are those which are easily
fusible and easily dissociated by heat. The halogen salts experi-
mented on by Sir J. J. Thomson were found to give a small excess
of positive electrification when heated, but nothing nearly so great
as that given by the phosphates.
Aluminium phosphate was the salt first used in the present
experiments, and tubes containing this were employed as anodes
in an apparatus (see Fig. 1) similar to that described by Gehrcke
* J.J. Thomson, Proc. Camb. Phil. Soc. Vol. xiv. p. 105.
+ Gehreke and Reichenheim, Ann. der Phys. xxv. p. 861, 1908. _,
VOL. XV. PT, IV. 22
330 Mr Horton, The emission of positive rays
and Reichenheim. The discharge tube was a round-bottomed
flask of some 500—1000 c.c. capacity. It was connected to a
mercury pump and McLeod gauge, and had a charcoal tube
attached for producing a low vacuum by means of liquid air.
Owing to the high melting points of the salts used in these
experiments, the tube A, which contained the anode, was of
fused quartz, 2 mm. internal and 5 mm. external diameter. The
aluminium phosphate to be used as anode was finely powdered
and mixed with a little powdered graphite to render it conduct-
ing, and also with a little silver chloride to bind the mass together
when heated. This mixture was rammed into the end A of the
quartz tube to a length of 2—3 cms. The tube was then strongly
heated in a blow-pipe flame. This caused the silver chloride to
melt, and on cooling the mixture was firmly held in the tube.
Electrical connection with this mixture was made by means of a
copper wire introduced into the tube at the other end and pushed
into the mixture while that was still hot. The cathode is the
aluminium ring K at the end of an aluminium wire, the straight
part of which is covered by a glass tube as shown in the diagram.
These tubes, from the anode and cathode, pass through holes in an
ebonite bung which closes the mouth of the flask, the joints being
made air-tight with sealing-wax.
The discharge through the tube was sent from a large Marconi
induction coil. It would have been better to have used a large
Wimshurst machine (following the method of Gehrcke and Reichen-
heim), but there was not one available. A spark-gap and a valve
of Lodge’s pattern were usually placed in the secondary circuit of
the coil in order to prevent, as far as possible, the current from
passing in both directions.
Perhaps it may be of interest to mention here that for obtain-
ing quickly the low vacuum required in these experiments, it was
found to be of great advantage to have the tube containing the
charcoal for cooling in liquid air made of fused quartz. During
the preliminary pumping a blow-pipe flame was played directly on
to the quartz tube, and in this way the charcoal was more quickly
and more completely freed from occluded gas.
When the induction coil discharge passed through this tube
(the gas pressure being so low that no luminous gas was seen in
the bulb) the “torch” of light at the anode, desctibed by Gehreke
and Reichenheim, was obtained. On examination, the spectrum
of this light was found to contain the brightest silver lines, but no
lines of aluminium could be detected. In a magnetic field part
of the luminosity was deflected in the direction which would mean
that the rays consisted of positively charged particles leaving the
anode, and partly in the opposite direction, but I could never be
quite sure that this was not due to the discharge from the coil
from heated phosphorus compounds. 331
passing in both directions. The light at the anode never showed
the fine bright pencils so characteristic of the anode rays, and
the spectrum proved that if any anode rays were produced they
were due to the silver chloride, and not to the aluminium
phosphate.
Other methods of making the aluminium phosphate into a
solid mass, capable of being used as an anode, without mixing
with any substance likely to produce anode rays, were tried, but
without success. It was therefore decided to use some more
fusible phosphate, and a mixture of sodium and lithium pyro-
phosphates with a little graphite was heated in the quartz tube
until it fused. This tube was then fitted up as the anode in a
bulb similar to that described above. On evacuating and passing
a discharge this tube behaved in a curious way. When the
pressure was not too low, there was a torch of light surrounding
the anode, in front of this a dark space, and then at about the
centre of the bulb a little ball of luminosity, which probably
corresponded to a striation in the positive column. On putting
on a magnetic field transverse to the direction of the rays from
the anode, the torch seemed to jump out nearer to the glowing
ball, at the same time spreading out symmetrically about the axis
of the anode, and curling round towards the cathode ring. The
appearance was as though a stream of rays were suddenly brought
up against a barrier. The effect produced seemed to be inde-
pendent of the direction of the magnetic field, so long as the lines
were at right angles to the direction of the discharge. That
sodium was shot off from the anode could be seen by the gradual
appearance of the yellow sodium light upon the cathode—appear-
ing at first on the side nearer to the anode and gradually spreading
all over it. The spectrum of the light at the anode showed the
lines of sodium and lithium brilliantly, also the brightest mercury
lines, including the three new lines in the orange the wave-
lengths of which are given by the author in a previous paper*
as 6232, 6121, 6070. .
In a more perfect vacuum the gas luminosity in the bulb
disappeared, but the glow at the anode remained. There was
however no sign of the fine pencils of light, with the accompany-
ing phosphorescence of the bulb, which is so characteristic of the
anode rays. In a magnetic field the glow at the anode was mostly
deflected in the positive direction, but there was some which
behaved as though it were negatively charged. In order to decide
whether the rays deflected in the positive direction were really
positively charged, or whether they were negatively charged rays
travelling towards the anode, their behaviour in an electrostatic
* Proc, Camb. Phil. Soc. Vol. xv. Pt 5.
22—2,
332 Mr Horton, The enussion of positive rays
field was investigated. For this purpose the apparatus dia-
grammatically represented in Fig, 2 was used. The rays leaving
A were made to shoot through the hole in the earth-connected ~
screen S, and then between the parallel plates P,, P,, which were
about 3 cms. long and placed about 1 cm. apart. A strong electric
field could be created between these by connecting them to the ter-
minals of a battery of small accumulator cells. Z is a zinc-blende
screen by means of the phosphorescence of which the deflection
of the rays could be observed even when the illumination along
their path was very faint.
Fig. 2.
A, anode, S, earth-connected screen. Z, zinc-blende screen.
C, cathode. P,, P,, parallel aluminium plates.
As with the former apparatus it was found that there was no
fine pencil of rays given off by the anode. The rays getting
through the hole in the screen S were always deflected towards
the positive plate by the electric field, showing that they were
negatively charged. They were, no doubt, ordinary cathode rays
formed by the reversals of the induction coil. The impossibility
of obtaining anode rays from these phosphates seems to show that
there is no connection between the anode rays and the positive
electrification emitted by salts when heated, but it was thought
worth while seeing whether anode rays could be obtained from
other compounds of phosphorus, because these, as well as phosphorus
itself, have the power of emitting positive ions when heated on
the anode of a vacuum tube.
Some experiments were therefore made in which calcium
phosphide mixed with a little graphite was used as the anode
in the apparatus of Fig. 1. At a low pressure a distinct torch
of rays was seen surrounding the anode, and, after a few minutes,
from the midst of this torch there came a fine pencil of rays
shooting right across the bulb and causing phosphorescence of the
glass where they struck. This pencil seemed to have its origin
at a spot on the surface of the anode which was hotter than the
rest of the surface. It was not deflected in a weak magnetic field,
from heated phosphorus compounds. 333
but was deflected in the positive direction in strong fields. These
rays were evidently anode rays similar to those obtained by
Gehrcke and Reichenheim. The spectrum showed some calcium
lines and other lines which could not be identified in the short
time during which the rays persisted. Thus we see that anode
rays can be obtained from calcium phosphide, although they could
not be produced from the phosphates experimented with.
Gehrcke and Reichenheim have connected the production of
anode rays from the halogen salts of the alkalis and alkaline
earths with their easy fusibility and their property of dissociating
when strongly heated. The heated salt is supposed to be decom-
posed electrolytically by the passage of the current, the metal
being liberated at the surface of the anode and travelling across
the tube. Close to the anode the electric force is very strong on
account of the anode fall of potential, and it is in traversing this
region that the liberated metal atoms obtain their great velocity.
Some time ago it was shown by Matthies* that the anode fall in
a vacuum tube was greatly increased by the presence of a halogen
vapour. In a recent paper Reichenheim states that, at low pressures
and with large currents, the anode fall in the halogens amounts
to several thousand volts. This abnormally high value Reichen-
heim thinks may be explained on the supposition that the halogen
vapours possess, in a higher degree than other gases, the power of
_absorbing negative electrons. If this be correct, other electro-nega-
tive vapours should behave in a similar manner, and Reichenheim
shows that a large anode fall is also obtained in phosphorus
vapour. In the experiments described in this paper it is probable
that phosphorus vapour was present in the case of the calcium
phosphide anode, owing to its decomposition when heated. There
would thus be a large anode fall and a strong force near the anode
which would give to the liberated atoms the energy to make them
luminous anode rays. The phosphates, on the other hand, are
extremely stable bodies, and in their case there would be no
phosphorus vapour to cause an abnormal anode fall and con-
sequently no anode rays. Thus these experiments seem to confirm
the view of Gehrcke and Reichenheim as to the origin of anode
rays, and to show that there is no connection between this pheno-
menon and the emission of positive electrification from heated
salts.
The author wishes to acknowledge his indebtedness to the
Government Grant Committee of the Royal Society for the means
of purchasing some of the apparatus used in these experiments.
* Matthies, Ann. der Phys. xvut. p. 473, 1905.
+ Reichenheim, Verh. d. D. Phys. Ges, p. 168, 1909.
334 Mr Orange, On the shape of beams of canal-rays.
On the shape of beams of canal-rays. By J. A. ORANGE, B.A.,
Senior Scholar of Trinity College. (Communicated by Professor
Sir J. J. Thomson.)
[Read 8 November 1909.]
In a recent paper* the writer stated certain conclusions with
respect to beams of canal-rays obtained in connection with
“sandwich-kathodes.” It was maintained that. the canal-rays
are straight, the curvature of the boundaries of the beam being
explained by supposing that they are merely the envelopes of
such rays.
This point has been tested since by using a mica obstacle and
observing the form of the shadow in the beam. The method
of placing the obstacle will be evident from Fig. 1, where m is
the mica slip, which is attached to the aluminium kathode-plates
by means of water-glass. The beams of canal-rays were photo--
Fig. 1.
graphed as described in the former paper. The sharpness of the
boundaries of the beams in the case of hydrogen was remarkable,
and a considerable degree of sharpness was obtained in the photo-
graphs, the softening that did occur being attributable to slight
changes in the form of the beams (due to changes of pressure)
while an exposure was being made. [The time of exposure was of
the order of 45 minutes.] Figs. 2 to 6 are copied from photographs
and illustrate the point at issue.
The outlines of the beams and of the Crookes’ dark space
at a fairly high pressure are shown in Fig. 2. For clearness’
sake, the shadows in the beams due to the three pins are omitted.
The beams will be referred to by the letters shown in Fig. 2. The
shadows due to the pins in Figs. 3 to 6 are in accordance with the
explanation adopted.
With regard to the effect of the mica slip, it may be as well
to say at the outset that the use of this is liable to serious
objections. If the mica slip were an obstacle only to the canal-
rays, the method would be much sounder; but since the mica
is a local obstacle to the discharge in general, its introduction
* J. A. Orange, Proc. Camb, Phil. Soc. Vol. xv. Pt. 3, 1909, p. 217.
Mr Orange, On the shape. of beams of canal-rays. 385
336 Mr Orange, On the shape of beams of canal-rays.
may produce great changes in the electrostatic field, which is
known to depend largely on the distribution of ions in the kathode
region.
Consider the effect of the slip in Fig. 3 in the light of this
reservation. Beam A, which we hold to originate in the lower
part of the region, (kathode-rays from the longest side of the
triangle being the primary agent), contains a sharp shadow as
shown. Here we can claim that the mica does not interfere at all
with the discharge from the longest side of the triangle, and hence
the beam A is formed normally, the mica simply blocking out
part of the canal-rays when they have passed through the kathodic
interspace.
But now consider the effect on beam B. Here we have to
deal with canal-rays produced in the N.E. corner of the region,
the kathode-rays from the medium side of the triangle being
responsible. The slip, however, is placed so as to interfere con-
siderably with the discharge (including the kathode-rays) from
this side. Thus instead of getting a neat shadow in the beam, we
get an ill-defined dark core which is vaguely indicated in Fig. 3 by
a dotted line of elliptical form.
The details of Fig. 3 are typical of the appearances for various
positions of the slip, as may be readily imagimed. The effect
of placing the slip in a more exceptional position is shown in
Figs. 4, 5 and 6, which correspond respectively to decreasing
pressures.
The general tendency is best shown at the lowest pressures,
e.g. in Fig. 6. The beams are roughly of the forms which would
be obtained if the right-hand corner of the kathode were
removed altogether, as indicated by the dotted line in Fig. 7.
This right-hand corner is certainly fenced off by the mica and
the pin so that it is prevented from acting as a double kathode;
the forms of the beams would seem to be in accordance with this
fact. The only other feature of interest is the fine pencil of canal-
rays coming from the aperture between the mica and the pin, and
visible in Figs. 4 and 5.
These observations would seem to support the view that
the constituent canal-rays are straight.
I wish to thank Prof. Sir J. J. Thomson for his kindly interest
in these experiments.
Mr Welsch. An Electric Detector, etc. 337
An Electric Detector for Electromagnetic Waves. By HK. M.
WELLIscH, B.A., Emmanuel College. (Communicated by Professor
Sir J. J. Thomson.)
[Received 6 November 1909. ]
A series of experiments in connection with ionisation produced
by collision was undertaken by the writer in order to test certain
theories which he- had previously advanced with regard to the
passage of electricity through gases. The preliminary experiments
were made with an ionisation chamber containing two parallel
plane electrodes made of aluminium, and at a distance from one
another of 2cm.; one of these electrodes was connected to a
source of potential, the other to a Dolezalek electrometer. During
the course of these experiments it was observed that, when the
gaseous pressure and the electric field were so chosen that the gas
was on the verge of breaking down, a very feeble discharge of a
Rontgen ray bulb placed in the neighbourhood was sufficient to
produce an exceedingly large deflection of the electrometer needle
which had previously been stationary; the direction of the de-
flection indicated the passage of a transient electric current
through the gas. Further investigation of this electric charge
produced within the gas showed, however, that the determining
cause of the deflection lay not in the rays issuing from the Rontgen
bulb, but in the electric oscillations set up by electric waves
proceeding from the induction coil which worked the bulb. The
Roéntgen bulb was henceforth removed and a series of experiments
was conducted in order to ascertain what degree of sensitiveness
to electric waves could be obtained from similar arrangements.
Several forms of ionisation chambers were used, and each of them
proved sensitive as detectors of extraneous electric waves. The
accompanying diagram represents the scheme of connections
employed in one of the trials. In this case the detector consisted
of a glass tube 7’ (about 4 cm. in diameter); the electrodes were
two plane parallel aluminium discs (each 2 cm. in diameter) at a
distance apart of 1 cm. The tube was connected to a Topler
mercury pump and a MacLeod gauge so that the pressure of the
gas (dry air) could be adjusted and measured. In the diagram B
represents the battery, one of whose poles is earthed, H the electro-
meter, & a high resistance (consisting of conducting glass) shunted
across the electrometer, C a variable capacity, and Z a variable
self-induction. i
The sensitiveness of the detector depends naturally on a large
variety of circumstances ; in fact, in the preliminary trials, it was
338 Mr Wellisch, An Electric Detector
found impossible to record the conditions present when a high
degree of sensitiveness had been obtained, so that it was a matter
of difficulty to reproduce these conditions ad libitum. However,
as a rough example of one set of conditions, it was found that with
the air at a pressure of ‘76 mm., and with one electrode connected
to the negative pole of a battery of 400 volts, the tube would
respond to faint electric impulses provided the capacity, resistance,
and self-induction were suitably adjusted ; the electrometer needle,
otherwise stationary, would be deflected on the arrival of the wave.
The object of the high resistance R was to cause the needle to
return quickly to its zero so that any succeeding impulse might be
readily detected.
The effect of an extraneous electric impulse is probably to set
up electric oscillations in the circuit including the vacuum tube;
the electric force in these oscillations, when superposed on the
electric field in the tube, may then suffice to produce a discharge
in the gas. It is important to notice that this discharge need not
be, and in most of the cases investigated was not, luminous; its
occurrence is manifested merely by the galvanometer or electro-
meter deflection. In this respect the present detector differs from
Zehnder’s Trigger Tube* in which the induced electric oscillations
precipitate an electric discharge from an auxiliary battery and thus
produce a glow in the tube. Another method for detecting electric
waves which depends upon the same principle is that due to
Boltzmannt. In this method a battery is on the verge of charging
* Wied. Ann. Vol. xv. 1892, p. 77.
+ Wied. Ann. Vol. xu. 1890, p. 399.
for Electromagnetic Waves. 339
an electroscope through a very small air-gap; electric waves in the
vicinity will be detected by the electroscope if they are able to
excite oscillations of strength sufficient to break down the spark
gap. In the Fleming Oscillation Valve induced electric oscillations
are detected by their ability to impart unilateral conductivity to
the space between a cold cylinder and a hot carbon filament, the
conductivity being due to the negatively charged corpuscles
emitted from the heated carbon under the action of a directional
electric force in the oscillations.
Comparative tests have been roughly made with the electric
detector and an iron filings coherer, and have proved quite
favourable to the former; a short period electrometer (e.g. the
string electrometer described by Laby in Proc. Camb. Phil. Soc.,
vol. XV.) seems especially suited for use in connection with the
present form of detector.
It was observed also that in ionisation chambers such as those
described, distinct deflections would occur under certain conditions
of pressure and voltage in the absence of any electric waves pro-
duced by the induction coil; as an example of one set of conditions
it was found that with the air at a pressure of ‘76 mm., and with
one electrode connected to the negative pole of a battery of 480
volts, frequent deflections occurred. The frequency of these deflec-
tions varied considerably with the inductance in the circuit ; in
fact, a small variation of the inductance changed the frequency
from about 100 to 12 deflections per minute. It is reasonable to
suppose that these deflections are due also to electric oscillations set
up in the circuit including the detector. The writer is making
further experiments with regard to these oscillations, especially
with the object of determining their origin.
340 Mr Fryer, Aldabra and neighbouring Islands.
Aldabra and neighbouring Islands. By J. C. F. Frymr, B.A.,
Gonville and Caius College.
[Read 22 November 1909.]
Puate XII.
| Abstract. ]
Introduction.
The group of islands comprising Aldabra, Assumption, Cosmo-
ledo and Astove is situated some 270 miles to the N.W. of
Madagascar and thus les in the extreme §.W. corner of the
Indian Ocean. Aldabra has long been known as the last spot
in the old world on which indigenous giant land tortoises continue
to exist. It was also known to have a peculiar land avifauna;
and these facts combined with the discovery of unusual percentages
of iron, alumina and silica in guano from the locality pointed
to a possible land connection with Madagascar in previous
times.
In 1905 the Sealark expedition carried on investigations in
the Indian Ocean relating partly to the former land connection
between India and Africa and partly to the formation of the coral
islands of this ocean. The Aldabra group however was not
visited and therefore from both points of view a further expedition
was desirable. Certain of the more general results of this latter
expedition are set forth in this paper.
Topography.
Aldabra is an atoll 24 miles long and from 4—10 miles broad.
The land-rim is very perfect and is divided by narrow passes into
four large islands called respectively Picard, Polymnie, Malabar, °
and Main or South islands. Round the outside of the atoll is
a narrow fringing reef which is divided by channels from the
passes and is indefinite or non-existent on the extreme east.
To landward the fringing reef is bounded by rocky cliffs
10—20 ft. in height which are overhanging and show evident
signs of wave erosion.
The highest point on the land-rim (20 ft. above sea-level)
is always situated near the sea-cliffs and there is a gradual slope
to the lagoon which is fringed with dense mangrove swamps.
Small overhanging cliffs are usually found at high tide mark
in the swamp and give striking evidence as to the rapidity of
lagoon erosion. The lagoon itself is very shallow except near the
passes ; it is muddy towards the outsides and sandy in the centre.
Small islands and rocks are numerous round its outskirts and all
show much loss due to erosion.
The general topography of the larger islands is as follows:
Mr Fryer, Aldabra and neighbouring Islands. 341
Picard is noted as possessing on its westward shore a narrow
stretch of sand on which is built the settlement and which also
constitutes the only arable soil on the atoll. In the centre of the
island is a rocky plain with a flat pavement-like surface: it is
known as Plain Cabris and is the locality from which were
obtained certain peculiar rocks to be referred to later. The rest
of Picard is more typical of the atoll as a whole; the surface of
the ground has been broken up by rain-water denudation into
points, pinnacles and sharp ridges, and the whole is covered with
a dense scrub of Pemphis acidula. This combination of rock and
jungle, known as ‘champignon’ country, forms the great bar to
exploration in Aldabra.
Polymnie, Malabar, and the north of Main island consists of
this champignon country. In the 8.E. of Main island however
another plain of flat pavement-like rock exists. It is covered
by a somewhat open and varied jungle, and within its boundaries
are found the only fresh-water springs on the atoll. These are
situated at Takamaka and consist of pits in the rock about
5 ft. deep. Sand dunes 60 ft. high occur along the south of Main
island and have been formed by the action of the prevalent winds
(S.E. Trades) which blow up sand from the reef and pile it in
mounds on the shore. The west of Main island is again entirely
of the champignon type of country.
Leaving now the general topography of the atoll a more
detailed account of its structure may be given, and this will be
dealt with under three heads, (a) structure of land, (b) structure of
fringing reef, (c) structure of lagoon.
Structure.
(a) The land is entirely rocky and the main rock component
is in all cases coral though complications have been introduced by
the presence of a quantity of calcium phosphate derived from
guano. The rock of the land-rim may be divided into three
classes. The first forms a zone round the outside of the land-
rim and is marked by the fact that its component corals are
very perfect and are almost all in position of growth. This point
is most important as 1t proves that the atell is an elevated reef
and that it has not been formed by wave piling on a subsiding
base. ‘The second class is the pavement-like rock before referred
to: 1t 1s composed of broken and often triturated coral with such
débris as mollusc shells and echinoderm spines, and gives evidence
that the mner portions of the reef before elevation were either
dead or but feebly growing. The last class of rock is the
‘champignon’; it is a highly metamorphosed coral rock with
scattered inclusions of calcium phosphate derived from guano.
Metamorphosed coral limestones from all the islands in this region
contain inclusions of calcium phosphate, and it is necessary to
342 Mr Fryer, Aldabra and neighbouring Islands.
credit the latter substance with some power of inducing meta-
morphosis though its nature is not understood. In all the three
classes of rock pits and subterranean caverns are numerous and
usually contain salt-water which fluctuates tidally. They all
show signs of erosion and are increasing in size. Evidence is thus
given that the reef as a whole before elevation was but badly
consolidated and that even now water can percolate completely
through the land-rim.
A few exceptional rocks remain to be dealt with. Ile Esprit,
in the lagoon, consists of a ridge of rock half a mile long and
some 30 ft. high, and is thus the highest rocky point on the atoll.
The body of the ridge consists largely of calcium phosphate :
on its sides are pinnacles and walls of a much denuded rock
composed almost entirely of mollusc shells. Plain Cabris on
Picard island again shows somewhat similar structures but a
crystalline mineral resembling apatite should be noted as also
fossil bones of the giant land tortoise. It may be mentioned
that Esprit island is of special importance if an attempt is
made to reconstruct the early stages of Aldabra after elevation.
(6) The second section of the atoll consists of the Fringing
Reef. Evidence obtained from the amount of wave erosion and
from rocks of elevated coral limestone still in situ proves that the
fringing reef of Aldabra is a ledge of elevated coral rock cut down
to low water mark and preserved at that point by growing
lithothamnia and by the piling of sand and coral on the fiat.
The fringing reef of Aldabra therefore is not a sign of the
increase of the atoll seaward, but on the contrary is evidence
of the loss of land owing to wave erosion.
(c) The last section of the atoll is the lagoon, some of the
features of which have already been mentioned. Those to be
further treated are the extent of lagoon erosion and the formation
of passes. Judging by the maze of small islands and rocks, once
part of the land-rim, at least’ two-thirds of the lagoon were at one
time land. It is still increasing for the rock is reduced to mud;
the mud is swept to sea and the land continues to diminish.
Contrasting lagoon erosion with sea erosion it will be noticed
that while the latter is uniform over any stretch of coast the
former is just the reverse, and is extremely irregular. Passes
therefore must be formed from the lagoon side of the land-rim
and not from the sea. All stages of pass formation are shown
on Aldabra. At Camp Frigate the mangrove swamp passes
completely through the land-rim to the sea, though but little
water flows through yet. The western channels show complete
passes through the land-rim but the fringing reef has not yet
been divided. Grande Passe finally is a pass with a complete
channel, and it further shows that the channels of the passes
Mr Fryer, Aldabra and neighbouring Islands. 343
do not increase indefinitely in size though the land continues
to be cut down as far as low water mark. This point will be
further illustrated by the atoll of Cosmoledo, which will be
described later. The structure of Aldabra has now been described,
and before proceeding further it may be mentioned that any
land connection with Madagascar is shown to be obviously
impossible.
The Flora and Fauna of Aldabra must be treated very briefly
for the collections are not completely worked out.
Flora.
The Flora contains, oecologically, the following sections:
(1) Pemphis jungle which grows on metamorphosed rock and
contains little but Pemphis acidula. (2) Open country jungle
which contains a varied vegetation of Madagascar origin. (3) Man-
grove swamp containing three genera of Rhizophoraceae and
also the pseudo-mangroves Avicennia, Sonneratia and Carappa.
(4) Shore zone containing typical coral-sand plants such as
Tournefortia argentea and Scaevola koenigii. The zone owes
its origin to the fact that sand is blown on to the land from the
reef and forms a little soil near the shore.
Fauna.
The Mammalia, as regards indigenous species, are represented
by two bats only, though one Pteropus aldabranus is peculiar.
Reptiles comprise the Giant Land Tortoise (Testudo daudinii),
the Green Turtle (Chelone mydas), the Hawksbill (Chelone
imbricata), two species of Gecko and a Skink. The distribution
of the Giant Land Tortoises affords an interesting problem. They
have been found in recent times on the Seychelles, the Mascarenes,
Madagascar, Aldabra, Assumption and Cosmoledo. Their presence
on continental islands such as the Seychelles is easily accounted
for by the previous land connection, but this explanation will
not apply to islands of purely oceanic origin such as Aldabra.
The fossil bones on the latter atoll appear to prove that they
do not owe their distribution to transport by man: they are at
present too large to drift on wreckage or logs, or if drifted before
their large size was evolved, then they present a wonderful case
of parallel evolution, The matter still awaits a satisfactory
solution.
Amphibia are absent from Aldabra and the fish though speci-
fically numerous call for no special mention.
The land invertebrata are at present being worked out but
it may be mentioned that the majority seem to be derived from
Madagascar: indeed it may be said that the whole land fauna
with the exception of the Giant Land Tortoise is such that it may
have been obtained from neighbouring lands without necessitating
any former continental connection.
344 Mr Fryer, Aldabra and neighbouring Islands.
Next passing to the other islands visited, a brief summary of
the chief structural characters of each may be given.
Assumption is not an atoll but is an elevated reef composed
of the same classes of rock as constitute the land-rim of Aldabra.
The rock is extremely cavernous; water can penetrate completely
through the land and there is no doubt that, as the caverns
inter-connect, the island will be broken up into a number of
rocks.
Astove is an elevated atoll with a very perfect land-rim which
is divided by only one pass. It is composed of the same three
classes of rock as were found on the land-rim of Aldabra, though
coral in position of growth is even more common. The lagoon
is very shallow and probably existed almost entire at the time of
elevation. It is getting larger; fresh passes are forming and the
atoll will be speedily broken up.
Cosmoledo is also an elevated atoll but differs from Aldabra
and Astove in having but half its circumference capped with land.
The remainder, the reef, is elevated coral rock cut down to low
tide level and piled with coral débris while the edge is protected
by growing lithothamnia. There is no doubt however that once
the whole circumference of the rim was land. Sand derived from
disintegrated rock is abundant and hides the rock of the islands
so that there is a tendency as the rock land is removed to replace
it by sand cays.
The state of Cosmoledo must be considered as forecasting in
part the future condition of Aldabra, and in conclusion an hypo-
thetical biography of the latter atoll may be given, basing the
account on the facts obtained from the various coral islands in the
region.
The geology of Aldabra shows that it is entirely of oceanic
origin and has been built up by active coral growth, and therefore
our history of the atoll must begin with its formation as a reef
beneath the sea. There must first have been, however, some
base or mountain-top which reached to within 40 fathoms of the
surface, for it is well known that reef-building corals cannot
live at greater depths. Of the nature of this base we have no
evidence, though it may be taken as probable that it is of the
nature of a volcanic mound. We know of volcanoes in the
Comoros to the S.W. and the Sealark dredged volcanic mud near
Providence to the E., and there is thus no inherent improbability
in the existence of volcanic action in between. However this may
be, it 1s necessary to assume the presence of some base, colonised
by corals, forming a reef which gradually grew up until it nearly
reached the surface. This may be deduced from the fact that
the fossil corals are all of a shallow-water facies. As to the form
of the reef we suppose both from the geology and from theoretical
Mr Fryer, Aldabra and neighbouring Islands. 345
considerations that the outsides were flourishing, while the inner
portions were but feebly growing or dead. This means that the
shape of the reef was probably that of a shallow basin.
The next point in its history was its elevation above the
surface of the sea, though how this occurred is somewhat doubtful.
It would naturally be supposed that it was accomplished by
a slight local elevation of the earth’s crust, but against this is the
objection that there is evidence of an elevation of equal amount
throughout the western Indian ocean, and it is difficult to conceive
of an alteration in the level of the earth’s crust which would be
so uniform over such a large area. The only alternative is an
alteration in the level of the sea, and it may be mentioned that
there are points in favour of this hypothesis though they are
of too indefinite a nature to bring up for discussion in this
paper.
The extent of the elevation may be placed at about 60 ft.,
for sprit island is 30 ft. high, and it is probable that the reef
hardly reached the surface before elevation, while since then an
enormous amount of denudation has occurred. After elevation
the whole reef was placed out of water and the depression in
the centre was dry. In Astove it will be remembered there was
evidence that the present lagoon was largely existing before
elevation, and may therefore be called a primary lagoon, while
in Aldabra we now see that the present lagoon must be a
secondary lagoon developed after elevation. The question of its
formation will be dealt with shortly, but first certain deductions
must be made from Esprit island which consists almost entirely of
calcium phosphate. The phosphoric acid was undoubtedly derived
from guano, and to have formed the phosphate rock on Esprit it is
necessary to suppose that a solution obtained entrance to a large
underground cavern which may have contained a certain amount
of sand or mud. The whole space was gradually filled with the
deposit, and to have obtained such a large quantity it is necessary
to suppose that the top of Esprit was the sink or drain from
a large area covered with guano. This area was probably the
primary lagoon which after becoming dry was filled with guano
by oceanic birds. For the present, therefore, it is supposed that
all the peculiar phosphate rocks of Aldabra were formed by a
solution of guano obtaining entrance to a subterranean pocket.
Turning next to the formation of the secondary lagoon,
mention was made of the fact that the rock as a whole is still
very cavernous so that water can penetrate completely through
the land-rim. At the time of elevation this feature must have
been more marked, and therefore the sea could at once begin
_ dissolving away rock and enlarging any spaces. Simultaneously
rain-water denudation was acting on the surface and the natural
VOL. XV. PT. IV. 23
346 Mr Fryer, Aldabra and neighbouring Islands.
result was a gradual decrease in level. In time the subterranean
caverns, becoming larger, joined each other and finally a series,
probably in the neighbourhood of Grande Passe, obtained open
connection with the sea. After this a tidal current swept in and
out continually dissolving away rock and forming a lagoon. The
transition from this stage to the present one is easy: a further
pass, Passe Houareau, next formed and the lagoon gradually
obtained its present dimensions, though Ile Esprit, on account
of its being composed of an insoluble rock, was left standing as
a clue to former conditions. The level of the land gradually
decreased by rain-water denudation and fresh passes continued to
form until the present state of things obtained. As to the future
we may safely prophesy the formation of more passes: lagoon
erosion will proceed with increased speed though it 1s noticeable
that land is only cut down to low tide mark, for below this
lithothamnia, corals and the piling of sand form a protection
against speedy erosion. Looking further into the future and
bearing in mind the present state of Cosmoledo we see that
the rock islands will gradually be divided up and be separated
from one another by long stretches of reef. The islands may
be eaten away until no land remains, though it is more probable
that it will continue to exist in the form of sand cays so character-
istic of many atolls. This stage may be called the Farquhar* stage.
Beyond this it is impossible to foretell; and in conclusion it may
be suggested that the life-history of Aldabra will be found typical
of most coral rock islands, and finally may give a clue as to the
former history of many of the coral sand islands so common in the
tropics.
* Farquhar atoll, 150 miles east of Astove, is in this condition. Vide Trans.
Linn. Soc., Vol. x11. p. 144.
Lin fs h fe
lmte emall Sixlareke
TABRA ISLAND
Spot + Lat. 9° 227.35 S._ Long. 46714. 41 E
Vartation tr 1905, dracasing about 8 annually.
land 4. R. PS. Champignon Rock and Pemphis Scrub.
le dott)
~ . os 5
S Leaner ae
S
ne
L A N D
Casuarin:
i ale
Mangrovee teh : 3 a .
biel Sa ene WN ase States SBP ER at
eee ia,
EP
emf
re
: : hig 3
mts mall hands iy
<3 Western
Ths avee ail about
Scattered
Coral
at Low Water
ad olted \
a3 ho tlt es $f ae
SS ASaPeS fe Petts
. Baraches Jorks. .
os Re er
A priate
z Ait pee 7)
. 2
J . suas : .
: 2 Be = ee eg o _ A¥dson’s Well
rt - a < Gee Tah u -
sv
‘Brugié YA ew
PET Penn
200
yruch alley ed
ast
AW thes stretch oye os
yance SUTY OT
g.
Cram Pignen Recht ;
And Pempbhie Jancie
he renal an
Obs) Spot + Lat, 97 22..45°S.— Long: a6" AVE
Maqneug
Variation in 1905, decreasing about B' annually,
5 Sea Miles
All soundings in fathoms. Figures on the land show the heights in feet above H. W. Springs.
ert. coral, 7. rock, s. sand, sh. shells, w. white.
Double dotted line=a main track, other tracks not indicated.
Single dotted line defines an area of land or lagoon.
ABRA ISLAND
uo
R. P.S. Champignon Rock and Pemphis Serub.
PLatE XII
*
Rieti
bas
-*,1
EAA all Po
4
5 phe
A
Mr Lillie, Notes on the Larger Cetacea. 347
Notes on the Larger Cetacea. By D. G. Liu, B.A,
Hutchinson Research Student of St John’s College. (Com-
municated by Mr A. E. Shipley.)
[Read 22 November 1909.]
The establishment of whaling stations within recent years in
three localities off the shores of the British Isles should give a
new impetus to the study of Cetology, and stimulate additions to
our knowledge of the larger Cetacea before these much-hunted
animals become too scarce. .
Hitherto our studies of these enormous creatures have been
chiefly derived from isolated specimens stranded from time to
time in various localities around the coasts of civilised countries,
which coming by chance into the hands of zoologists, often in
an advanced state of decay, have enabled them to add a few
observations to the large though scattered Cetacean literature.
This would indeed seem the only method possible since, during
the last three centuries, the whaling imdustry has been confined
to the wildest regions of the earth and carried on under conditions
of physical privation which were beyond the endurance of all but
a few.
Since the whaling industry of to-day now supplies fresh
material fairly near at hand, and is destined to play a large
part in any new work which may be done on the histology and
general biology of whales in the near future, it will not be in-
appropriate here to briefly trace the history of this industry from
early times until its establishment near our shores at the present
day, and to give a short account of modern methods of whaling
before proceeding to record an observation of more. strictly
scientific interest, which was made during a preliminary visit
to the Irish whaling station in the past summer.
In very early times whales occasionally became stranded just
as they do now, through venturing too near the shore and being
left high and dry by the tide. It was, no doubt, soon discovered
that the oil of these stranded individuals could be utilised; but
the practice of pursuing and killing large whales, as far as is
known, only dates from about the year 875 s.D., the Basques
then hunted Balaena biscayensis, and from their word “ arpoi,”
which means “to take quickly,’ we get the word “harpoon.” At
first the Basques attacked this whale from the shores of the Bay
of Biscay ; but they later put out to sea on long voyages as the
quarry became scarcer.
This fishery was practically exhausted by 1607 when Henry
Hudson made his first voyage to Greenland and Spitzbergen and
discovered the Greenland whale (Balaena mysticetus) in its home
23—2
348 Mr Inllie, Notes on the Larger Cetacea.
among the northern icefields. The English and Dutch immediately
opened up the Arctic whale fishery, taking with them the hardy
Basque seamen to act as their instructors. This fishery reached
its height at the beginning of the 18th century, English, Dutch,
Germans, Spaniards and Danes all taking part. In 1749 the first
vessels set out from Scotland and took over the fishing in Davis
Strait, while the Americans worked that of the Behring Strait,
the fishery on the east coast of Greenland being then exhausted.
The last great names associated with the Greenland fisheries are
those of Scoresby and David Gray in the Atlantic and Scammon
in the Pacific. The fishery is now almost extinct.
In 1712 the Sperm whale (Physeter macrocephalus) was first
hunted. This fishery was started by Americans on the island of
Nantucket in the Atlantic. British ships took part in 1775 and
extended the fishery to the Pacific and Indian oceans, but they
abandoned it in 1853. This whale is now chiefly hunted by
Americans and Norwegians.
The shore-loving Californian Gray whale (Rhachianectes glaucus)
was first pursued on the Pacific coast of North America in 1846.
In 1866 a new era began in the whaling industry. Up to this
date attention had necessarily been confined to the two species of
Balaena, the Sperm whale and the Californian Gray whale. All
these slow-moving creatures could be hunted with the hand
harpoon in small boats each manned by six men, which put
out from the shore or from a whale ship in mid-ocean as soon
as a whale was sighted.
The fast-swimming Balaenopteridae or Rorquals remained
unmolested by man until 1866, when Captain Svend Foyn, a
Norwegian seaman, invented a harpoon which made their capture
possible. This deadly projectile is fitted with an explosive shell
and is fired, together with the attached harpoon-rope, from a gun
in the bow of the whaling steamer. Captain Foyn took out a
patent for his invention, established a station at Vads6 and opened
up the Rorqual whale fishery off the coast of Finmarken.
In 1882 his patent expired and numerous stations sprang into
existence along the northern coasts of Norway and Lapland, after-
wards spreading to Iceland and the Faroe Islands.
In 1903 this industry reached the shores of Scotland. There
are now four stations on the mainland of Shetland and one in
North Harris in the Hebrides. In 1908 a station was established
on the Island of South Innishkea off the coast of Co. Mayo in the
west of Ireland and a second Irish station is expected to open next
summer. All the stations on the east side of the Atlantic are in
the hands of Norwegians who, like the old Basque whalers before
them, are the masters of the industry they invented and have
been engaged by other nations to teach them their craft. The
A
Mr Inllie, Notes on the Larger Cetacea. 349
result has been that modern whaling centres have sprung up in
Newfoundland, Japan and elsewhere.
The staple quarry of the northern whale fishery is the widely
distributed family of the Balaenopteridae, the last of the larger
Cetacea, the Sperm whale and Balaena biscayensis being also taken
when they can be found. The Balaenopteridae are still fairly
plentiful but, at the present rate of slaughter and with the
rapid spread in the use of the deadly Svend Foyn harpoon, the
day of their extinction cannot be far distant, as Mr Shipley pointed
out in his presidential address to Section D at the Winnipeg
meeting of the British Association.
The Norwegian method of whaling is briefly as follows. A
station is established on shore or afloat to which three or four
strongly built steamers from 15 to 90 tons burden are attached.
Each has a harpoon gun mounted in her bows. These go to sea
in search of whales and stay out from two to ten days at a time.
When a steamer gets within 40 yards of a whale the harpoon is
fired, and the shell at the point of the harpoon is so arranged that
when the harpoon enters the body of the animal it bursts and the
animal is generally killed at once; but this is not always the case.
Mr Southwell records an instance of a whale, Balaenoptera
sibbaldi, towing a Newfoundland whaling steamer for a distance
of 122 miles, the screw being reversed at full speed the whole
time. After a pursuit which lasted 26 hours the animal was
exhausted and killed.
The Balaenidae and Physeter float when dead; but the
Balaenopteridae always sink, probably on account of their having
less oil, The Norwegians have overcome this difficulty by an
ingenious device. The dead whale is brought to the side of
the steamer and inflated with air. An iron pipe is thrust into
the body cavity and is connected by india-rubber tubing to a
pump in the engine-room. When sufficient air has been pumped
into the body cavity to render the animal buoyant, the pipe is
withdrawn and the wound is plugged with a piece of tarred wood.
In this condition the dead whale is kept afloat, and several can be
towed to the factory at one time by a whaling steamer. The air
thus pumped in keeps the carcase distended until it is landed and
ready to be cut up, its volume being sometimes added to by the
gaseous products of decomposition. As soon, however, as the dis-
tended body is pierced by the flensing knife the imprisoned air
escapes with great violence and portions of the viscera are torn
away and shot out of the body cavity. The two foetal whales
which I obtained this year at the Irish whaling station were
extracted in a mutilated condition from among the scattered
remains of organs thus expelled from the body cavities of their
mothers.
350 Mr Lallie, Notes on the Larger Cetacea.
Directly a whale is hauled up the slip or landing stage the
whalebone and the blubber are rapidly stripped off and the latter
boiled to extract the oil. The remainder of the carcase is dragged
asunder by means of wire ropes and steam winches and cut up by
many hands. The bones and soft parts are roughly separated,
dried and ground in mills to form bone manure, flesh manure,
cattle food and, at some stations, various forms of preserved meat
for human consumption. In this way a whole animal 70 feet long
and as many tons in weight will often disappear completely in the
course of a morning.
To the scientific man a whaling station does not pretend to
offer the advantages of unlimited time and comfort which are to
be found in a laboratory. It is so essential, in the whaling trade,
to dispose of the animals as rapidly as possible while the oil is
fresh that the whalers can hardly be expected to wait for the
deliberations of the anatomist. Yet there can be little doubt
that to visit a whaling station such as the one in the west of
Ireland is a more satisfactory method of increasing our knowledge
of the larger Cetacea, than to depend upon the occasional stranding
of an isolated specimen on some part of the coast. For at a
station all the largest whales, with the exception of Balaena
mysticetus and Rhachianectes glaucus, can usually be seen within
the space of three months. Very frequently several individuals
of different species can be examined and compared as regards
their external characters and their internal characters also,
according to the skill of the investigator in overcoming the
obvious difficulties arising from the manipulation of such large
creatures. The material is often sufficiently fresh for histological
study, which, on account of the gigantic size of the animals, should
prove of considerable interest. Moreover exceptional opportunities
occur for observing the animals in the living state.
With regard to the smaller Cetaceans, since they are seldom
killed by man, material is difficult to obtain; but the study of
these animals is not at the moment so pressing as that of the
rapidly decreasing larger forms.
It now remains to briefly record one of the several observations
which were made at the Irish whaling station, during a visit of
seven weeks, in the past summer.
The distribution and significance of the scanty hairs of the
Cetacea do not appear to have been hitherto studied in the detail
they deserve. They have been vaguely referred to as occurring on
the lower jaw of some adult forms. Sometimes they have been
found on the foetus only. 7
In two adult Sperm whales (Physeter macrocephalus) seen at
Innishkea this summer, no trace of hairs could be found on any
part of the animals even after careful searching.
4
Mr Lnllie, Notes on the Larger Cetacea. 351
In the case, however, of the Rorquals Balaenoptera sibbaldu
and Balaenoptera musculus some ten individuals of each species
were examined and it was found that a definite distribution of
hairs could be made out in each case. Four rows of white, bristle-
like hairs from half an inch to an inch in length occur on the
dorsal surface of the beak or facial region of the head. These
consist of two inner rows on either side of the median ridge which
bears the blowholes or external nares and two outer rows following
the edges of the snout, from points just behind the blowholes to
its anterior extremity. The average number of hairs in each row
is about eight.
On each side of the lower jaw there was a row of some five or
more hairs running from the tip of the mandible along the middle
line of the outer edge of each ramus to a point just im front of
the eye. At the extreme anterior end of the mandible, over the
ligamentous junction of the rami, there were also two rows of hairs
set at right angles to those above mentioned. These occur close
together and run parallel to each other from the upper to the
under surface of each ramus. The hairs in these two rows are
placed closer together than in the others, there being generally
about fourteen hairs in each row.
On looking through the Cetacean literature there appears to be
no record of the occurrence of hairs in the odontocetes, except in
some foeti. It would seem that the presence of hairs in the adult
is restricted to the whalebone whales and their retention and
distribution over the beak and mandible in these forms may
be due to their possessing a tactile function and thus serve to
indicate to the animal the presence of its food.
The small size of the organisms, which generally form the food
of the Mystacoceti, making them difficult to see, and the olfactory
organs of the Cetacea being very reduced, it seems reasonable to
suppose that the occurrence of tactile hairs over the oral region
would be a distinct advantage, as the small food animals would
brush against them and thus inform the whale when to open its
mouth. The top of the snout of a whale is, after all, only the
prolonged upper lip, where one would naturally look for vibrissae.
The food of the odontocetes being of a larger size the presence of
tactile hairs 1s not obviously required, and so the hairy covering
has entirely disappeared in the adult forms of these whales. If
the hairs of the whalebone whales do not function as suggested
above, an interesting problem remains open to solution to explain
how these animals become aware of the presence of their food.
352 Mr Southerns, Experimental Investigation as to Dependence
Experimental Investigation as to Dependence of the Weight of
a Body on tts state of Electrification. By L. SouTHERNS, B.Sc.
(London), Whitworth Scholar, 1851 Exhibition Scholar. (Com-
municated by Professor Sir J. J. Thomson.)
[Received 9 December 1909.]
In a previous paper* the writer described an experiment
designed to detect any alteration which might occur in the weight
of a body when its temperature was changed. The present paper
deals with an experiment which seemed naturally to follow the
former one, viz. an attempt to detect change of weight due to
electrification. This experiment, unlike the other, appears to give
a positive result. The object of the experiment is not to actually
weigh electricity, but rather to find whether the presence of
electricity on a body modifies in any measurable degree the force
of gravity acting upon it. While such a modification of gravity
seems to provide the simplest way of explaining the results, such
explanation is by no means insisted upon. Further reference to
this matter will be made in the last section of the paper.
The paper is divided into the following sections:
(1) General theory and method of experiment.
(2) Description of apparatus.
(3) Detailed description of experiments and results.
(4) Conclusion.
(1) General theory and method of experiment.
A general idea of the method employed may be gained from
consideration of fig. 1.
* Proc. Roy. Soc. A, Vol. uxxvit. December 20, 1906.
v
of the Weight of a Body on tts state of Electrification. 353
Suppose a delicately but stably-balanced earthed conductor A
to be placed between two fixed charged conductors B, C, at
potentials + V,, — V, respectively. Two electrostatic fields F,, P,
will be set up, and these will be quite independent of each other,
provided all lines of force from B to C are intercepted by the
conductor A, which is at zero potential, or by some other earthed
conductor. Charges will be induced on the ends of A, which will
now be subject to electrostatic forces which will in general deflect
it to a new position inclined at an angle, say 0, from its original
equilibrium position. If now the fields F,, F, be reversed each
independently of the other, so that we have B at potential — V,
and C at potential + V,, there will be no change in this deflection
@ caused by electrostatic forces, for these are independent of the
direction of the fields. But now let us suppose that a gravitation
effect exists such as to cause the end of A, which is positively
charged, to be a little heavier than the negatively charged end.
This will give a deflection +6 which must be added to 6, thus —
with one direction of field we shall have a total deflection 6 + 6,
and with the direction of field reversed we shall have deflection
§@—6. The difference between the two observed deflections will
thus be 26, the electrostatic part of the deflection being eliminated.
In observing deflections practically two methods may be adopted.
We may observe the zero position under no field, then put on the
field in a given direction and observe 0+, discharge and _ re-
determine zero, then charge in the opposite direction, and observe
@—6 and take the difference. Or we may disregard the zero and
merely, having the field in a given direction, observe position of
A, then reverse the field and note the deflection 26 which results.
Both these methods have been used.
It will be seen that there is no theoretical necessity for making
the fields or the conductors symmetrical or the potentials V,, V,
numerically equal to each other. In practice, however, it is
desirable to make the apparatus and fields as symmetrical as
possible, though it is quite possible to obtain results with wide
differences between the potentials V,, V,. With symmetrical
apparatus the deflection 0, due to electrostatic forces, will be
small and any deflection due to a gravitation effect will be more
readily observed.
The form of apparatus indicated in fig. 2 is therefore adopted.
The beam AA with its curved end pieces is supported by a steel
knife edge and grooved plate by means of which it is electrically
connected to earth. The pierced guard cylinder D, and metallic
case H, are also earthed. The field plates B, C are insulated
and connected through a double reversing key to the sources of
potential, which are separate for the two plates. Some of the
354 Mr Southerns, Experimental Investigation as to Dependence
lines of force from these plates fall on the guard cylinder and on
the case. The apparatus can be adjusted so that the forces acting
on AA are very nearly horizontal, so that they produce only a
very small deflection from the uncharged position. This deflection
is usually made small for practical convenience, but the resulting
value of 6 is the same for large as for small deflections. The
stability of the arrangement and method of determining sensitive-
ness while under the electric field will be referred to later. It
may be mentioned here that variations of weight corresponding to
soy OF zadop Mm. are easily detected in practice.
This method of arranging the apparatus and of applying and
reversing the fields eliminates several errors which might be
expected to cause difficulty in an experiment of this nature. As
shewn above, the effect of electrostatic forces (which do not depend
Fig. 2.
on the direction of the field) is eliminated on reversal. The same
also applies to any heating effect due to currents which pass while
charging and reversing, or to leakage currents, and also to electro-
magnetic effects, none of which depend on the direction of the
currents or fields. A point which has often been mentioned to the
writer is the difficulty of eliminating stray lines of force. These
are really unsymmetrical portions of the field which go to make
up the deflection @ as described above and are included in the
preceding discussion. Experiment shews that great departures
of the Weight of a Body on its state of Electrification. 355
from symmetry do not vitiate the result. Thus the field plates
may be moved, or we may use either of the plates alone, the other
being earthed, or we may adjust the beam in such a way that 0
is large or small and in either direction from the zero. In all
these cases the result is unaffected*. In most of the experiments
the balance was screened from any possible external electrostatic
effects, this however made no difference to the result—stray lines
coming on to the beam from the external electrical apparatus gave
rise to no discrepancy, these will be dealt with more fully when
the experiments themselves are described. The effects do not
depend on strict accuracy being attained in the magnitude of the
potentials employed. A variation of eight volts out of a thousand
purposely introduced produced no effect on the results. This
shews that the results are not due to some variation of potentials,
such as might be caused by contact difference.
Reference will be made later to some effects observed with
electrometers which seem to have a bearing on the subject, but it
should be borne in mind that the present instrument is not an
electrometer, indeed it is the exact opposite, that is to say it is
designed so that electric charges produce the least possible de-
flection instead of the greatest as with the electrometer.
(2) Description of apparatus.
The apparatus was for the most part+ constructed by the writer
(who was aided by a Royal Society grant) at the Technical College,
Huddersfield, and afterwards set up in the Cavendish Laboratory,
Cambridge. The general plan of the arrangements is shewn in
fig. 3.
In the figure, A represents a table standing on rubber blocks
and supporting the main instrument or balance B which is enclosed
in a wooden box. C is a table on which are placed an observing
telescope D, a scale H, with its sliding support and lamp F, a
double pendulum electroscope G, a multi-cellular voltmeter H,
keys J, K, L, M, Daniell cell NV, and resistance box P, the uses of
which will be described later. Another table # carries a cabinet
of 1000 small secondary cells in two separate trays of 500 each,
which are connected to the key Z by the leads 7. The diagram
is approximately to scale, the distance from telescope to balance
being about two and a half metres. The dotted lines represent
connecting wires which are insulated on paraffin wax columns.
* Trregular fluctuations occur in the magnitude of the result, but they are
extremely small for an experiment of this kind.
+ Knife edges by Oertling.
356 Mr Southerns, Haperimental Investigation as to Dependence
Fig. 3.
of the Weight of a Body on its state of Electrification. 357
The balance itself is shewn in fig. 4. It is rigidly made so
that the applied electric forces shall not produce distortion. The
case, guard cylinder, field plates and beam are constructed of
magvalium. Referring to the figure, AA represents the beam
with its arresting arrangements aaa, B one of the end pieces, CC
the guard cylinder and D# the insulated field plates. The beam
is electrically connected to the guard cylinder by means of its
steel knife edge which bears on a grooved steel plate attached to
bescos
N
RQ
Saag
Fig. 4.
a pillar screwed to the guard cylinder. The object of the groove
in the bearing plate is to prevent side slipping of the knife edge
under the action of the electric forces. The guard cylinder itself
is rigidly fixed to the back of the case, and the whole earthed by
means of the earth wire shewn in fig. 3. (It should be noted that
all the earth connections are made with one wire as shewn in that
figure.)
It will be seen from the figure that a small amount of play is
allowed between the piece B and the guard cylinder. This allows a
358 Mr Southerns, Experimental Investigation as to Dependence
few lines of force from D to pass between the two, and some of these
will terminate on the edges of B. Those falling on the upper and
lower edges in the figure give rise to forces tending to deflect the
beam. If everything is symmetrical these forces will be equal
above and below, and therefore the beam will not actually be
moved. But if B is slightly higher than its central position, the
lower gap will be wider than the upper one and more lines of
force will therefore fall on the lower edge of B than on the
upper edge. These will tend to bring B back again to its central
position. The beam is always in stable equilibrium under the
action of the field. The application of the field, however, affects
to a slight degree the sensitiveness of the apparatus as a balance,
and it is therefore necessary to have some means of determining
the sensitiveness while the field is on. This is provided by the
arrangement shewn in the upper part of the figure. It is an
adaptation of a method employed in a balance designed by
Dr Hicks and used by the writer in the research previously alluded
to. A small and feeble magnet is attached to the beam as shewn
by the dotted lines at F. This can be attracted or repelled by a
small current passing round the coil G. The deflection produced
by a given current can be compared once for all with that pro-
duced by moving a rider a certain distance along the bar H. By
observing the deflection produced by this current during an actual
experiment with the plates charged, the sensitiveness can be
determined, and the value of any deflection produced by the
charges expressed in mgms. of weight. The current is not of
course allowed to pass during actual observations. The current
required to produce a measurable deflection of the beam, though
small, is vastly in excess of any possible leakage current between
the field plates in the balance, and therefore it is impossible that
these should act directly on the magnet and give rise to any
difficulty by causing deflections. The cell, resistance and key,
N, P and M in fig. 3, are used for supplying the current. The
rider is not moved during a series of observations. It is used
before observations are commenced in order to level the beam.
By suitably levelling the beam the electrostatic deflection 6 may
be varied at will, both in magnitude and direction. Many values
of this deflection have been used in the experiments.
The deflections are observed by telescope and scale, and a
double suspension mirror, the position of which is indicated by the
circle K. The field plates D, H are insulated by sulphur plugs
and have various adjustments not shewn on the figure. Other
details, such as knife edge adjustments, etc., are also left out of
the figure to avoid complication. The front and back of the case
are of thick magnalium with plate glass windows. The latter
have been covered inside with tinfoil in the later experiments,
4
of the Weight of a Body on tts state of Electrification. 359
with the exception of a small space for observing the mirror K
which has been closed in with a grid of fine wire. The results,
however, are exactly the same whether the windows are covered
or left bare. The whole apparatus is enclosed in a box of wood
2 inches thick and provided with double windows of plate glass.
The diagram is approximately to scale. The diameter of guard
cylinder is 14°3 cms., distance between this and field plates 3 mms.,
the end pieces B, which are square with rounded corners, 4°9 cms.
square. Weight of end pieces about 28 grms. each, total weight
of beam about 260 grms.
TS
Fig. 5 is a diagram of the keys K and L of fig. 3. Lisa
bvatfin block with mercury cups and connections as shewn. The
cups A, B are connected to the negative and positive terminals of
the top tray of cells and C, D to the negative and positive terminals
of the bottom tray. # and H are connected to two other cups Q,
R, which are permanently connected to the electroscopes and to
the key J in fig. 3 by wires S, 7. The wires U, V to the balance
can be dipped into the cups Q, & by means of the lever W to
Fig. 5.
360 Mr Southerns, Experimental Investigation as to Dependence
which they are attached. The cups /’, G are permanently earthed
by the wire X. By means of a rocker not shewn in J connections
can be made as shewn by the dotted lines, two kinds of dots being
used to shew the connections corresponding to the two positions
of the rocker. The mercury in the cups B, C, N, O is higher than
that in the other cups in order that earth contacts shall always be
made before and broken after high potential contacts. It will be
seen that the key simply consists of two ordinary six cup reversing
keys fastened together. The lever W is used to throw the balance
connections in or out as desired. It will easily be seen that the
arrangement here described satisfies the condition that the two
fields F,, F, of fig. 1 shall be quite distinct from each other. By
means of the key J in fig. 3 the multi-cellular voltmeter H can be
connected to either of the wires S, 7’ in fig. 5 at pleasure.
(3) Detailed description of experiments and results.
The several experiments will now be described in order and
their results afterwards discussed.
1. June 9th, 1909. (Used 1000 volts on each side of balance
in all cases except when otherwise stated.) There was very large
electrostatic deflection 0, no attempt being made to reduce this,
The zero of balance was altering rapidly. In the following tables
the observations are numbered, and the arrows shew the position
of the rocker of reversing key (refer to tig. 5). The column
marked 26 is calculated from three successive readings, it is the
difference between the mean of the first and last of the three and
the intermediate reading.
A. Front cover of balance off.
Scale Scale Readings used for 93
Readings Readings calculation of 26
V t
1 48:2 2 47:4 IS he) 1:25
3 49-1 -4 48-9 2, 3, 4 0:95
By Bylo Gin D053 3, 4, 5 1:20
4, 5, 6 1-25
Mean 1-16*
* See Table on p. 369 for values of 6 corrected for sensitiveness.
of the Weight of a Body on tts state of Electrification. 361
B. Front cover of balance off.
Scale Scale Readings used for 95
Readings Readings calculation of 26
y ft
| rs 325) Rete 85
yo MOO) 3) 2058 De oe 1:10
4 588 5 58-0 3, 4, 9 1:40
On 9°6 4, 5, 6 1:20
Mean 1:14
C. Cover on. (The larger windows are coated with tinfoil.)
| |
Scale Scale Readings used for 28
Readings Readings calculation of 26
| i
1 80:2 2 80-0 12S 1°35
3 82°5 4 82:2 2, 3, 4 1:40
5 84:2 (fai) 3, 4, 5 1:15
7 860 8 85:2 4, 5, 6 1:15
BB, 0 1:20
6, Ue 8 1:45 |
Mean 1:28
2. June 10th.
A. Electrostatic deflection large, but not so large as in last
expervment.
Scale Scale Readings used for 25
Readings Readings calculation of 26
V t
i 6750 2 66:0 as) 0:75
3 6625 4 65°6 2, 3, 4 0-70
5 662 GeenoDsS oy 45° 0:75
4, 5, 6 0-75
Mean 0:74
VOL. XV. PT. IV. 24
362 Mr Southerns, Experimental Investigation as to Dependence
B. Taken at 1 minute intervals. Reversed at 4 minutes.
Seale Scale | Readings used for 23
Readings Readings calculation of 26
Y f
1 65:9 2 64:9 Pee) 0:80
Si Ga 4 64:9 2S, A 0:60
i OOH 6 64:8 3, 4, 5 0:65
i NDE 8 64:9 4, 5, 6 0:75
DeOn ag 0-85
6, 0,78 0:85
Mean 0-75
C. Smaller electrostatic deflection, zero for no field 120°0 about:
Scale Scale Readings used for 28
Readings Readings | calculation of 26
| t
i nye 2 14-9 igo 1:35
ay 16! Reales) 2, 3, 4 1:00
Ig) G Waewv | 3, 4, 5 1-20
4, 5, 6 isis
Mean 1:17
D. Cut out and earthed balance, and moved over reversing
key several times. No change of zero.
3. June 12th.
A. Taken at 1 minute intervals. Zero about 63:0.
Scale Scale Readings used for 95
Readings Readings calculation of 26
4 f
1 26-9 eee 8 1:05
2 27-0 3 25-0 Doe 1-25
4 25:5 > 24:1 3, 4, 5 0:95
Mean 1:08
of the Weight of a Body on its state of Electrification. 368
B. Put 4 volts in and out of one battery of cells. This
made no appreciable difference to the deflections.
C. Zero about 52°5.
Scale Scale Readings used for 25
Readings Readings calculation of 26 =
| i
1 -2:2°8 a) Divo Ly 2, 3 1:25
B) | ve I| 4 20:8 2, 3, 4 1:10
5) Dhlery 3, 4, 0 1:10
Mean 1:15
D. Zero taken between reversals. Observations at-1 minute
intervals.
Readings used
Seale ‘ Seale Ton ‘ :
Readings a Readings 2800 eres ae
) t
ez 4: YB Bygeat 3) BOs AD 22 I yD 1:15
Dy Pall) 6 92°3 2 3 Oy Of 1:25
Mean 1:20
E. Put 4 volts in and out of one battery. The only effect was to
alter the electrostatic deflection @ in the ratio 4: 1000. This
alteration was about 0°1 scale divisions.
4. June 14th.
A. Zero about 60°5. Electrostatic deflection in opposite
durection to last.
) gave 72:3 { gave 71:3 (about).
B. Put 8 volts in and out of one battery, no perceptible
difference in deflections,
24—2
364 Mr Southerns, Experimental Investigation as to Dependence
C. Very small electrostatic deflection and zero steady.
Seale Scale Readings used
Zero Readings 288 Readings sO a
t 1
199°0n 2) 00st 39858 4) LOO 2,-4.6 0:95
i OY || GOO) MIS PS OTE LEN Os ts 1:00
9598-79) 10 100,05 ISOS os a2 00.9 6, 8, 10 1:00
13 98:5 | 14 99-8 |15 98:3 |16 100-7 8, 10, 12 0:95
10, 12, 14 1:00
12, 14, 16 1:00
Mean 0°98
D. Reversed without taking zero.
Scale Scale Readings used for 25
Readings Readings calculation of 26
Y f
lOO sG Dy RI} Ws 0:90
ay NOWer/ ho OSs 7 2, 3, 4 0:95
Mean 0:92
5. June 17th. Covered all the remaining windows with
tinfoil, except for a small space for observation of mirror, in this
and following experiments.
A.
Scale Scale Readings used for 9
Readings Readings calculation of 26 e
|
Geel ice 212823 IL PES} 0:65
3) PAS) 4 128-9 Day ey a 0:60
5S LOSS 7/ 6 129-5 3, 4, 5 0:55
4, 5, 6 0:50
Mean 0:57
of the Weight of a Body on its state of Electrification.
B. Zero about 71:0.
Reversed as rapidly as possible.
Scale Scale Readings used for 23
Readings Readings calculation of 26
i
25-0 2 124-9 We 2 ee 0:55
a) 129-9 4 125°8 2, 3, 4 0:55
5 126-6 6 126:3 3, 4, 9 0:45
mote Sle 2 4, 5, 6 0:55
OOM 0°65
Grin 0:55
Mean 0°55
6. June 18th.
Reversed connections of balance on the lever
Effect should be in
M. Kept all other connections as before.
opposite direction to previous effects, which is the case.
A.
Scale Seale Readings used for 29
Readings Readings calculation of 26 ty
ft /
Je tS4955) Oy tilly) IL) 8) 0:60
By eye) AL ei o7/ 2, 3, 4 0:70
5 82:1 By Ae 1) 0:60
Mean 0°63
ky
7. June 19th. Balance connection reversed as yesterday but
only one side of balance used, the other being earthed. Should
give half previous effects.
A. Left side of balance used. Observations at 1 minute intervals.
Scale Scale Readings used for 28
Readings Readings calculation of 26
f |
1 107-0 2 106:3 ee aes) 0°50
a L062 4 105:7 2, 3,4 0°20
5 105°6 6 105-0 3, 4, 5 0°20
4, 5, 6 0°25
Mean 0:24
366 Mr Southerns, Experimental Investigation as to Dependence
B. Right side of balance used.
Scale Scale Readings used for 23
Readings Readings calculation of 26
cz f | |
Es JUDE I ESS} 2 atO:s ey ie) 0-45
3) Ute ASS ITOSS 2, 3, 4 0-55
BR AUG) Ore Oe? 3, 4, 5 0-60.
4, 5, 6 0-65
Mean 0:56
8. July 10th. Balance connections in normal position.
A. 1000 volts each side as usual. Observations at 1 minute
entervals.
Scale Scale Readings used for 95
Readings Readings calculation of 26
j
1 103:2 2. Oat 1, 2,3 1:40
3 02:2 AalO259 mae. ab 1:30
ee One? 6 102°0 3, 4, 5 1:20
4, 5, 6 1-25
Mean 1:29
B. 660 volts each side.
Scale Seale Readings used for 25
Readings Readings calculation of 26 rs
f ¥
Ey 1033 2 lOS:8 ee) eae)
on LOZ 4 102% 2, 3, 4 1:15
SOE hy illo hers 3, 4, 5 NG
4, 5, 6 1:10
Mean 1:11
of the Weight of a Body on its state of Electrification.
C. 330 volts each side.
Readings used for
calculation of 26
367
26
Scale Scale
Readings Readings
f |
1 1033 | 2 1033 1,
3 1020 | 4 102-0 2,
5 100-7 | 6 100-7 3,
4,
9. July 16th. 800 volts.
Right plate of beam covered
(except near edges) with shellac varnish. That side of balance
only used, the left side being earthed.
Scale
Readings
|
1 14°5
3 14:3
5 14:0
Scale
Readings
2 14:0
4 13°8
6 13°3
Readings used for
calculation of 26
He 9 BO
~
Ore So bo
.
~
v
~
o> Ot H Co
26
0-40
0-40
0°35
0-45 -
Mean 0°40 .
Corrected to) ,.-,
1000 volts } pee
368 Mr Southerns, Experimental Investigation as to Dependence
10. July 19th. Used left side only. A wire was passed
through case and bent inside into proximity with the field plate
and end piece of beam, but without touching them. This could
be connected to one terminal of a Daniell cell, the other terminal
being connected to balance case.
A. Wire not connected to cell.
Scale Scale Readings used for 95
Readings Readings calculation of 26
y f
1 7:2 2 6°8 I, 20 0:40
Di thease + 7:0 2, 3, 4 0-30
5 U3 6 7:0 3, 4, 5 0:25
7 1:2 8 6°9 4, 5, 6 0:30
9 7:3 5B lOe. 0:25
Os 0:25
U5 oy © 0:35
Mean 0-30
B. Wire connected.
|
Seale Seale Readings used for 95
Readings Readings calculation of 26
Y f |
2 2 6°9 eye 3) 0:30
3 U2 4 6:8 2, 3, 4 0°35
5 7:2 6 6:8 3, 4, 5 0:40
4, 5, 6 0-40
Mean 0°36
of the Weight of a Body on tts state of Electrification. 369
Summary of Results, corrected for Sensitweness.
- Deflection 26 Sensitiveness Electrostatic Reduced
Number of : ‘
Exp pate i ees Rene ee deflection ae of
scale divs. x mgms.
A. LAlG 700125 "0007
B. 114 A very large 0007
C. 1-28 is 0008
A.
B.
C.
A. 1:08 00125 — 38 ‘0007
C. 15 ¥ ~ 30 0007
D. 1-20 ‘ ~ 30 00075
AC. 0:98 00167 +1 0008
ID) 0:92 rs about 0008
kee JA, 0:57 00200 + 54 ‘0006
iB: 0:55 9 + 54 700055
poe A. | 0-63 | -00250 +42 0008
(one 0:24 00222 0003 *
B. 0°56 700182 + 22 "0005
850 0A. 1:29 00200 — 20 0013
B. eral 00154 700085 |
C. 0:65 00125 0004 |
Tee |) 0.30 00200 | ape: | WOU “|
fake: eal 0-30 00333 0005
B. 0:36 4 0006
* The values of 6 in experiments 7—10 are not directly comparable with the
previous values, as various charges were used, as described above, in those experi-
ments.
24—5
370 Mr Southerns, Experimental Investigation as to Dependence
It will be seen from the above results that a positive effect
is constantly exhibited, constant in direction and as uniform in
magnitude as can be expected when regard is had to the nature of
the experiment, and the fact that the effect only represents a
difference of a few ten thousandths of a milligramme. Indeed it
is surprising that the fluctuations are not much larger. Some
preliminary experiments, in which the sources of potential were
charged Leyden jars, gave similar results, though they were more
irregular on account of the leakage of the jars. They shewed,
however, that changes in the adjustment of the apparatus which
were constantly made, had no influence on the average values of
the results.
From Experiment 8 A, B, C it will be seen that the effect—
so far as measurements of the actual magnitude can be relied on
—is proportional to the induced charges or to the potentials of the
field plates.
A few possible sources of error may be briefly alluded to:
1. Haternal electrostatic action due to lines of force entering
the balance case from outside. The fact that the front of the
balance case may be on or off (Experiment 1) or the windows
coated with tinfoil, or left bare without sensibly altering the result,
seems to shew that this source of error is inoperative. It is hardly
possible that it could be otherwise, for electrostatic effects de-
pending on the external conductors from key to balance would be
eliminated on reversal, and any permanent field which might exist
which could send stray Hines on to the beam, would merely give a
permanent deflection which would not alter the value of 26 on
reversal of the fields F,, F,, unless these stray lines penetrated to
the surfaces of the end pieces where the induced charges resided.
An examination of the drawing will shew how unlikely this is to
be the case. Moreover the shape of the surfaces is such that very
few of the lines so reaching them would tend to deflect the beam.
If the result had been due to direct action of the cells, voltmeters,
or other parts of the electrical apparatus, other than the conductors
mentioned above, it would have changed sign in Experiment 6
when the balance connections were reversed, but this was not the
case.
2. Mechanical operation of turning the reversing key. In
Experiment 6 the result would have changed sign had it been
caused by this operation. Moving the key produced no disturbance
of the balance.
3. Accidental variations in the potentials applied. Actual
variations of four and eight volts made no perceptible difference
to the results. See Experiments 3 B, #, 4B. These variations
were much greater than any which could have occurred during the
majority of the experiments.
of the Weight of a Body on its state of Electrification. 371
4. Small permanent fields inside the balance case. The
remarks under 1. above apply to this case also. In order to test
directly Experiment 10 was tried, in which a small field was pur-
posely introduced. The small effect recorded is within the limits
of experimental error, as an examination of the actual observations
will shew. Asa matter of fact, no movement whatever of the scale
could be detected when the field was put in or out.
5. Surface effects of the pieces carrying the induced charges.
In Experiment 9 one of the end pieces was coated (except near
the edges) with shellac, and this end of the apparatus only was
charged. It was feared that the shellac might give rise to electro-
static difficulties, but none were experienced, thanks no doubt to
the approximate symmetry of the apparatus. It is probable that
the field plate was a little further from the beam than usual in
this experiment. The result was the same as in Experiment 7 B,
when the same side of the apparatus was used. The value in
Experiment 9 is probably a little low (perhaps 1 in 5 or 6) due to
the suspected increase in the distance between the plates, but
the similarity of the results shews that these are not caused by
any peculiar action of the metal surfaces.
Some other sources of error, such as heating and electro-
magnetic effects, have already been dealt with.
(4) Conclusion.
Whether the effect be due to a modification of gravity or not,
the experiments appear to shew that a body, positively charged
with 20 electrostatic units of electricity, behaves as though it were
heavier than the same body negatively charged, by an amount of
the order of ‘0007 mgms. If the effect be due to a change in
gravity, there will exist in an electrostatic field a small amount of
energy due to this cause, and this will involve a very slight
alteration in the configuration of the lines of force from that given
by ordinary electrostatic laws. This would be so small as to pass
unnoticed in ordinary cases. It would be such that with given
conductors charged in a given way and then reversed as to sign of
charge, we should obtain two slightly different configurations of
field. Delicate instruments might detect this, and it is possible
that the different zeros of a quadrant electrometer, with the needle
positively and negatively charged, and quadrants earthed, may be
due to this cause, though the writer has not investigated these
effects, for the explanation of which the above suggestion may be
quite madequate. |
It was suggested to the writer that the effects might possibly
be caused by an accumulation of air condensed on the surfaces
of the metal, the quantity bemg greater when the surface was
positively than when negatively charged. Experiment 9 was
372 Mr Southerns, Experimental Investigation, ete.
really made in view of this suggestion, but from the point of view
of energy it would appear difficult to explain the result in any such
way as this. For we may liken the metal surface to a series of
buckets which are filled with condensed air, when the surface is
charged positively, but empty when it is charged negatively.
Now if we have a number of such surfaces, fixed to spokes,
radiating from a central axis so as to form a kind of wheel (like
a water-wheel) and place this between charged field plates, we
should have all the buckets on one side full and those on the other
side empty, and the wheel would revolve. It is difficult to see
where the energy would be drawn from to keep up this rotation.
It may be of interest, as a mere speculation, to see whether the
theory of gravitation which supposes that the attraction between
unlike charges is somewhat greater than the repulsion between
like charges, could be modified to suit the present results. Let us
suppose that the repulsion between two positive units at a given
distance apart is P, and that between two negative units NV, and
that the attraction between a positive unit and a negative unit is
M. Then the attraction between a neutral body (containing a
unit of positive and a unit of negative electricity) and a positive
unit will be JJ —P, and that between the neutral body and a
negative unit M—WN. The difference between these will be
N-—P, which is the effect found in the experiments. Again the
attraction between two neutral bodies (each containing one positive
and one negative unit) will be 2M@—(P+WN) and this will be
ordinary gravity. The last expression is much smaller than W—P
and thus we should have the result that while WV and P both differ
considerably from M, their mean is very nearly equal to M. Since
in the attraction M one charge of each kind is employed, it is
perhaps not unnatural to suppose that this might be the case.
The actual differences between M, N and P would of course be
exceedingly small in comparison with their absolute magnitudes.
Assuming M to be the ordinary electrostatic attraction, we have
two equations for finding Vand P. It should be remembered that
in the experiment, as in this theory, no lines of force pass between
the attracting masses. In the experiment the lines do not pass
to the earth, but sideways to the field plates. Turning aside from
such hasty speculations, the writer would be most grateful for
suggestions as to possible sources of error in the experiments, as he
hopes to have an opportunity of repeating them later with im-
proved apparatus, the design of which might be modified in view
of any suggestions thus made.
In conclusion the writer desires to express his thanks to Sir J.
J. Thomson and to Professor W. M. Hicks and DrS. R. Milner
for valuable criticisms and for the kindly interest which they have
taken in the experiments.
Miss Pearson, Note on an Attempt to Detect a Difference, etc. 373
Note on an Attempt to Detect a Difference in the Magnetic
Properties of the Two Kinds of Ions of Oxygen. By Miss D. B.
PEARSON. (Communicated by Prof. Sir J. J. Thomson.)
[Recewwed 11 November 1909.]
During the past year attempts have been made to discover
whether a magnetic field effects any separation of ionised oxygen
into its positive and negative constituents. Were such a separation
detected it wouid point to a difference in the magnetic properties
of the two kinds of ions.
The method of experiment was briefly as follows. Oxygen,
ionised by passage through a long tube lined with uranium oxide,
was passed between the poles of a strong electro-magnet and then
into a Faraday Cylinder connected to a Dolezalek Electrometer.
At first the gas was driven steadily through the apparatus with
the electro-magnet not active. The charge going to produce the
electrometer deflection was then merely that due to the excess of
one ion over the other, produced by the difference in the rates
of diffusion of the two kinds of ions. Readings of the rate of
deflection of the electrometer needle in these circumstances were
taken. Then the magnetic field was put on across the tube,
through which the oxygen was passing, and observations of the
movement of the needle once more made. If one ion were more
magnetic than the other it would have had a greater tendency
than the other to get into the region between the pole-pieces
of the electro-magnet, where the field was strongest. Consequently
the gas beyond this region would have been poorer in the more
magnetic ion, and this dearth of one of the charged constituents
of the gas reaching the Faraday Cylinder would have affected the
rate of deflection of the electrometer needle.
As a matter of fact, numerous observations gave no certain
indication of any effect produced by the magnetic field. All the
readings were small and variable, both with and without the
electro-magnet active. The means of the two series of readings
were, however, so closely concordant that the results may be fairly
taken to shew that the difference between the magnetic properties
of the two kinds of ions of oxygen, if it exists, is beyond the limits
of accuracy of the method used.
It would be out of place here to discuss in full quantitative
results, but it will perhaps be well to refer to them shortly. The
electrometer deflections were of the order of 3:5 scale divisions
374 Miss Pearson, Note on an Attempt to Detect a Difference, ete.
per minute whether the magnetic field was off or on. Such a
deflection was found to be produced if, in the conditions of the
experiment, 5°5°/, more of one ion than the other reached the
Faraday Cylinder. Although an exact limit cannot be set, it is
certain that a readjustment of ions sufficient to change the rate of
deflection of the needle by ‘5 scale divisions could not have escaped
detection. The magnetic field used cannot therefore have pre-
a of Boe
— 35 O o /
escaping beyond it to the cylinder. The magnetic field employed
was found to be about 6000 gauss at its maximum, and its greatest
rate of variation was 5000 gauss per centimetre.
vented more than ‘8 ions of either sign from
o}
Prof. Thomson, On the theory of the motion, etc. 375
On the theory of the motion of charged Ions through a Gas.
By Sir J. J. THomson, Cavendish Professor of Experimental
Physics.
[Read 8 November 1909.]
In the usual method of calculating the velocity of a charged
ion through a gas, the expression = * for the velocity is obtained
on the assumption that the ion after each encounter with a
molecule of the gas starts afresh and is as likely to move in any
one direction as the opposite. The momentum communicated to
the ion by the electric field in the interval before a collision
is assumed to be transferred to the molecule of the gas during
that collision, from which it follows that the maximum velocity
communicated to an ion by the electric field is that imparted
to it in the short interval between two collisions. It seems clear
however that the time during which the velocity is acquired
by the ion is the average time during which the ion continues
to move in one direction and not the time between two collisions,
and the time taken for an ion to have its motion reversed by its
collision with the other molecules may be much greater than the
time between two collisions. This will certainly be the case if
the mass of the ion is considerably greater than that of the
molecules against which it strikes. For let us suppose that the
average kinetic energy of the ion is equal to that of the molecules.
Let m be the mass of the ion, u its velocity, W and v the corre-
sponding quantities for the molecules, then since
mu = Mr?,
mu v m
Mv u M’
ioe :
i times the momentum
of the molecule against which it strikes and so the ion will have
thus the momentum of the ion will be
to collide with at least 5 a = molecules before its motion is re-
versed. From this it would appear that the quantity % which
appears in the expression for the mobility of the ion should be,
not the ordinary free path, which depends only on the size of the
ions and molecules and not upon their masses, but that free path
multiplied by some fraction of > ; if we call A, the ordinary
free path, the expression for the mobility would be
ery /m
mu M’
where p is a numerical coefficient which we have not determined.
376 Prof. Thomson, On the theory of the motion
If the absolute temperature is 0
amu? = a,
where a does not depend upon the nature of the ion or of the gas.
Thus the mobility will be
CNo
P /2Ma6’
i.e. it will not depend upon the mass of the ion except in so far as
mass is an indication of size, and since A, diminishes on this view
as the size of the ion increases, \, would depend to some extent on
the value of m.
It must be confessed however that in this as in many other
problems the methods founded on the mean free path leave much
to be desired, and are far less satisfactory than the method
introduced by Maxwell when he replaced the idea of collisions
between hard elastic spheres by that of the effects produced by
forces exerted by one molecule on another. Maxwell gave a
complete solution when these forces are repulsions varying in-
versely as the fifth power of the distance. It happens that on
the simplest view we can take of the forces between a charged
ion and a neutral molecule, i.e. that these forces are due to the
attraction between the electric charge on the ion and the dis-
tribution of electricity induced by this charge on the molecules
regarded as conducting spheres, these forces will vary inversely as
the fifth power of the distance unless the ion gets close to the
molecule. For the attraction between an electric charge e and an
unelectrified conducting sphere of radius a is equal to
ea? (2f? —_ a’)
Ge
(see Thomson’s Electricity and Magnetism, 4th edition, p. 154),
where f is the distance between the charge and the centre of the
molecule; when / is a considerable multiple of a, this expression is
approximately
2e’a8
ae
and thus varies inversely as the fifth power of the distance between
the ion and the molecule. In this case the force is an attraction
while Maxwell considers the case of a repulsion. Maxwell’s
investigation can be applied to the case when the force is attractive
with hardly any modification, the only change that is required
is in the numerical constants which Maxwell denotes by A;, A;;
these have not the same values for repulsion as for attractive
forces, since they depend on the magnitude of the apsidal
distance; with this exception Maxwell’s results can be applied
of charged Ions through a Gas. Ota
without modification to the case when the forces are attractive.
Maxwell gives an expression for the coefficient of diffusion of one
gas A into another 5 of the form
ee Mm, + Mz 1
2h mm,K A,(v,+ 2)’
where m,, m,. are the masses of the molecules of A and B, 1, vp
the number of these molecules in unit volume, K the force at
unit distance and h=N/2p, where p is the pressure exerted by
a gas in which there are N molecules per cubic centimetre,
h= : where & is a constant and @ the absolute temperature of
Dip =
the gas. A, is a numerical constant, having when the forces are
repulsive the value 2°659. Suppose now m, is the mass of a
charged ion the preceding equation wil] give us the coefficient
of diffusion of the ion through the gas, if we change the value
of A, to allow for the force being attractive, and put K = 2¢a’,
where a is the radius of a molecule of the gas B. We can eliminate
a by means of the relation
T
be ma 1 — N 4, a’,
where p, is the index of refraction of the gas B when there are
NV of its molecules per cubic centimetre. In the case of an ion
diffusing through a gas, v, may be neglected in comparison with v,
so that
D SE eich af 8rN
SOY) Mm, eC (fe — 1) Ayr.
The mass of the charged particle only enters this expression
Mm + Ms,
through the term , thus when the mass of the charged
1
particle is small compared with the mass of a molecule of a gas
through which it is diffusing, the coefficient of diffusion varies
inversely as the square root of the mass of the ion; if however
the mass of the ion is large compared with that of the molecule
the coefficient of diffusion varies exceedingly slowly with the
mass of the charged ion. Hence it seems to me that we can
attach but little value to the determinations of the atomic weight
of the emanations made by measuring their rate of diffusion
through air or hydrogen, for if these were positively charged
heavy particles the rate would be practically the same whether
the atomic weight of the emanation were 200 or 2000, though
this objection would not apply to methods based on the diffusion
through porous plugs.
378 Prof. Thomson, On the theory of the motion
The mobility of an ion, ie. the speed with which it moves
through the gas under unit electric force, is connected with the
rate of diffusion of the ion by the equation
RETO a
where 7 is the pressure due to V molecules per cubic centimetre.
Hence g
Tis ee ic iD
V MMe fo — 1 Ayr.
We see from this that the mass of a heavy ion has not much
effect on its mobility; the mobility of an ion consisting of a charged
molecule of the gas through which it is moving is 1/2 times the
mobility of one whose mass is very much oreater than that of a
molecule of the gas; the mobility does not however depend on the
charge on the ion. The velocity, through hydrogen, of an ion made
of a molecule of hydrogen charged with electricity, would be about
half as much again as that of a charged molecule of methyl iodide
_ through hydrogen and so would easily be distinguished from it.
Mobility of an ton through a mixture of gases.
If we have a small number of charged molecules A diffusing
through a mixture of gases B and C we can readily prove by
Maxwell’s method that D, the coefficient of diffusion of A through
the mixed gases, is given by the equation
1
= EE re MM, Ms J rae i . e ae 7 Mm, Ms = 2?
mM, + Mz 8S7N *MV im + ms ;
where v, and vy; are respectively the number of molecules of
B and C present per unit volume, m,, m, the masses of the
molecules of these gases, w, and m; the indices of refraction
of these gases when there are NV of their molecules per unit
volume. ae
The mobility & of the ion through these gases is given by
1
Jie ie
a My My = Ba M,Msz — —l
M+ My oy + Mm, + Ms
Let us consider the application of this equation to the es,
ments lately made by Mr Wellisch on the mobilities of the ions
through mixed gases and calculate the difference between the
mobilities through the mixture of charged molecules of B and
¢
of charged Ions through a Gas. 379
C. Mr Wellisch has proved to a high degree of accuracy that
in these mixed gases there is only one mobility. Let us take
the case of O, and SO, investigated by Mr Wellisch and cal-
culate the velocity (1) of an oxygen ion consisting of a charged
molecule of oxygen, and (2) that of an ion of SO, consisting
of a charged molecule of SO,; let us suppose that the partial
pressures due to these gases are the same so that »,=v,. If m,
is the mass of an oxygen molecule, m, that of an SO, molecule,
M,=2m,, and ‘w,—1="00038, 4;,—1=-00066; substituting these
numbers we find that the velocity of a charged oxygen molecule
through the mixture would be about 15 per cent. greater than
that of a charged molecule of sulphur dioxide, a difference which
could easily have been detected in Mr Wellisch’s experiments. If
the ions from oxygen and sulphur dioxide had been much more
complex than the single molecule of these gases their mobilities
through the mixed gases would have been much more nearly
equal than for the simple ions, and the difference in this case
might have escaped detection.
We shall consider in the light of the expression given above
for the mobility the various views that have been taken of the
nature of the ion. There are two main points to be considered
with regard to the ion, (1) is the ion more complex in structure
than a molecule, i.e. does it consist of an aggregation of molecules,
and (2) can the electric charge on the ion leave the ion and find
another home, thus producing a new ion, or is the charge bound
by an indissoluble bond to the molecules forming the ion. It
would seem clear from the great increase in the mobility of the |
negative ion which takes place in flames that the negative charge
must be able to leave one ion, exist for a time as a corpuscle and
then form a fresh ion: the question then is confined to the
positive ion, and we have to consider whether or not a positive
charge, carried by something much more massive than a corpuscle,
can leave one positive ion, unite with a molecule of the gas, and
form a new positive ion. If there were no transference of charge
from the positive ion, then if the positive ion was a single
molecule or even two or three molecules, there would in mixtures
of gases be two sets of positive ions moving with speeds sufficiently
different to have been detected in experiments like those made by
Mr Wellisch. Wellisch made some other experiments where a
small quantity of methyl iodide was mixed with a large quantity
of hydrogen, and it was found that the velocity of the positive
ions (which had originated from the methyl iodide) through the
mixture was the same as that of the positive ion through pure
hydrogen when the ion had originated from the hydrogen. If the
positive ion in hydrogen had been a single molecule of hydrogen
the velocity of the positive ion in pure hydrogen would be 1/2 times
380 Prof. Thomson, On the theory of the motion, ete.
the velocity in the mixture instead of being equal to it. We may
therefore conclude that if there is no transference of the charge
the mass of the ion must be a considerable multiple of that of the
molecule.
We must therefore consider whether the hypothesis of
complex positive ions is sufficient to explain the results which
have been obtained as to the mobility of the positive ion. The
expressions given for the mobility shew that when the mass of
the ion is large compared with the mass of a molecule of the gas
through which it 1s moving the mobility of the ion will be
independent of the electric charge carried by it, practically
independent of the mass of the ion, and at constant pressure will
vary directly as the absolute temperature, and will be inversely
proportional to the Vm(«—1), where m is the mass of a molecule
of the gas through which the ion is moving and yw its refractive
index. The result that the velocity is independent of the charge
and mass of the ion and depends only on the nature of the gas
through which the ions are moving is not in accordance with the
results obtained by Professor H. A. Wilson for the mobility of
ions in salted flames, for he found that the velocity of the
positive ions when salts of the alkaline earths were placed in
the flame was but little more than half the velocity of the positive
ions when salts of the alkali metals were placed in the flame.
Again though, as Mr Phillips’ results shew, the law that the
mobility at constant pressure is directly proportional to the
absolute temperature is very approximately obeyed at moderate
temperatures, it breaks down altogether at temperatures as high
as those which occur in flames. Thus the experiments of H. A.
Wilson and Moreau shew that at a temperature of about 2000° C.
the velocity of the positive ions in flames impregnated with salts
of the alkali metals is about 60 cm./sec. for a potential gradient
of 1 volt per centimetre; the velocity of positive ions through
air at 0°C. is about 1:4 cm./sec., so that the velocity at 2000° C.
would if it were proportional to the absolute temperature be
12 cm./sec., which is only one-fifth of the actual value. The rapid
increase in mobility with temperature is what we should expect if
the positive charge could, like the negative, pass from one molecule
of the gas to another.
CONTENTS.
PAGE
On the Oscillations of Superposed Fluids. By H. J. PRIDSILEY. _ (Com- ess
municated:- by W. WELSH.) ~(One fig. in Text) = i «UA ete
Discontinuities in Laght Emission. By Norman copes - (hres a ee
fies, ine Dext hf hy eee Si ee. le eae ee
The emission of positive rays from ened. “phosphorus CONE By. ;
Frank. Horton. (lwo fies«in Text) $5 Se 2 ee
On the shape of beams of canal-rays. By J. A. ORANGE. -(Communi- eae
cated by Professor Sir J. J. THomson.) (Seven figs.in Text) . 334
An Electric Detector for Electromagnetic Waves.. By E. M. WEuuiscu.
- (Communicated. by Professor- Sir J. J. THomson. ? oo a Mm em
Text PSS Ans : - 337
Aldabra and neighbour ug lane iy I Gs P hee Plate XII) RE BAO”
Notes on the larger Cetacea. BY DG: LILtin. eee ae
A. E. SHIPLEY) ; ; p : S47
Experimental snvestigation as to Depoitionce of the Weight of a Body on
its state of Electrification. By L. SoutHERNs. (Communicated by
Professor Sir J. J. THomson.) (Five figs. in Text) . Sie . 852
Note on an Attempt to Detect a Difference in the Want Properties
of the two kinds of Ions of Oxygen. By Miss D. B. PEARSON. mos
- municated by Professor Sir J.J. THomson) . : 5 313
On the theory of the motion of char. ge lons through a Gas. By Brotaeor :
Sir J/U. Laomson Co (Sg bee ee ee
- PROCEEDINGS
- CAMBRIDGE PHILOSOPHICAL
: | SOCIETY. |
wa
VOL. XV. PART V.
*
[Lent TERM 1910.]
Cambridge ;
AT THE UNIVERSITY PRESS,
; AND SOLD BY :
DEIGHTON, BELL.& CO, AND BOWES & BOWES, CAMBRIDGE.
cor ¢
Soe CAMBRIDGE UNIVERSITY PRESS,
C. F. CLAY, MANAGER, FETTER LANE, LONDON, E.C.
1910
Price Two Shillings and Stapence
14 June, 1910.
= NO TICES.
i Aelia oe Sn ‘sets of the frst, Sconces
Volumes (in Parts). of the Transactions should be made to eS
Secretaries of the Society.
2. Separate copies of certain parts of Coluniee I.—XI. of ike : : =
- Transactions may be had on application to Messrs Bowes G
- BowEs or. Messrs Deicuton, Bett & Co. Cambridge. -
3. Other Se of the Transactions may be obtained at
the following prices: Vol. x11. £1. 10s. 6d.; Vol. xit1. £1. 9s. 6d: ;
Vol. xiv. £L. 17s.-6d. ;-Vol. xv £1. 12s. 6d: ; Vol. xvi. £1. 10s. Od.:
~ Vol. xvi. £1. 2s. 6d-; Vol. xvut. £1. 1s. Od. ; Vol. XIX. £1. 5s. Dds
Vol. xx. £Y.-10s; 0d. Vol. xx1.-No:1, 3/-; No. 2 2, 4/-5 Nos. Zand
4, 1/6; Nos. 5 and 6, 3/-; No. 7, 2h het See
No. 10, 1/6; No. 11, 1/6.
4. Complete sets of the’ Prices Volatnee Se
may also be obtained on application to the Secretaries of the ©
_ Society.
5. Letters. and Gimummicaione for the Society should be
addressed to one of the Secretaries,
Mr A. EL SHIPLEY, Christ’s Polis. tBiological)
Dr E. W. BaRNEs, Trinity College. [Mathematical]
Mr A. Woop, Emmanuel College. [Physical.] _
6. Presents" foc the Library of the a should ee —
dressed to
-The Philosophical Libr ary,
; New Musewns, :
_ Cambridge. oe
T. Authors of papers are informed that the Illustrations aed 5 a
Diagrams : are executed as far as possible by photographic. “process”. ae.
work, so drawings should be. on a large scale and on smooth whi a
Bristol board 1 in. Indian ink,
8. Members of the Secicae are requested to inform the ss
: Secretaries of any, change of address.
PROCEEDINGS
OF THE
Cambridge Philosophical Society.
On the relative velocities of diffusion in aqueous solution
of rubidium and caesium chlorides. By G. R. Minss, B.A.,
Fellow of Sidney Sussex College. (From the Physiological
Laboratory, Cambridge.)
[Read 24 January 1910.]
In the course of some physiological work with the chlorides of
the alkali metals certain results led me to inquire as to the
relative rates of diffusion of these salts in aqueous solution. While
many data are available regarding the salts of lithium, sodium,
and potassium, I have been unable to find any figures relating
the two rarer members, rubidium and caesium, to the rest of the
roup.
2 The method I have used offers certain advantages in the
simplicity of the manipulations involved and the small quantity
of material needed for a determination. I therefore publish this
short account in the hope that it may be of use to others.
Graham* showed nearly fifty years ago that sodium chloride
diffuses in a gelatine jelly as quickly as in distilled water.
Voigtlindert found that the rate of diffusion of salts in agar-
agar was unaffected by changes in the strength of the jelly
from 1°/,—5°/,.
My plan has been to keep a solution of salt of known concen-
tration in contact with a free surface of jelly, and to ascertain the
rate of progress of the salt by measurement of the electrical
conductivity at a fixed distance below the surface of the jelly.
* Thomas Graham, Phil. Trans. 1861, p.
+ Voigtlander, Zeitschr. Physik. Chem, a “1889, p- 316.
VOL. XV. PT, V. 25
382 Mr Mines, On the relative velocities of diffusion in
The apparatus employed for this purpose is depicted in fig. 1.
It consists of a resistance cell of special shape. The platinum
electrodes are fused into opposite points in the wall of a glass
tube fifteen centimeters long and thirteen millimeters in internal
diameter, about twenty-two millimeters from the lower end,
which is sealed. During an experiment the mouth of the tube is
Fig. 1.
closed by a cork pierced by a short tube in which slides the glass
plunger P. This is prevented from turning by the piece of
cork C, which, gripping the plunger and sliding loosely on the
rod R, acts as a guide. The plunger is raised and allowed to drop
every two minutes by a wheel moved by clockwork and having
two pins projecting from opposite spokes in the same direction as
the axis.
aqueous solution of rubidium and caesiwm chlorides. 383
Five cubic centimeters of a warm 4°/, solution of well washed
gelatine* were introduced by a pipette and allowed to solidify.
The cell was immersed in a water bath kept at 18°C. The
resistance of the jelly was determined by the telephone method,
using a post-office resistance box; the alternating current was led
off from the primary of a small induction coil, the secondary being
connected in series with a 10 c.p. lamp to the 50 volt, 90 ~, house
supply.
The resistance of the jelly was not affected by standing in
contact with distilled water for over three hours: it is therefore
certain that the progressive changes in conductivity observed when
salt solutions are substituted for the water are not complicated
by the diffusion of impurities away from the gelatine. The salt
solutions used were deci-normal. 10c.c. of the solution were
poured on the jelly, filling the cell to the level indicated in the
figure, and the resistance of the gelatine between the electrodes
was measured, usually at intervals of half an hour, for the next
eight or ten hours.
The specific conductivity was obtained for each reading by
dividing the constant for the cell (643) by the resistance in ohms.
From this the specific conductivity of the gelatine at the beginning
of the experiment was deducted, the result indicating the specific
conductivity due to the salt. The molecular concentration of the
- salt corresponding to each of these values was read off from curves
constructed from the figures given by Kohlrausch+ and his co-
workers. At the dilutions with which we are concerned the
specific conductivity is very nearly in linear proportion to the con-
centration.
On plotting the concentrations against the times from
the beginning of the experiment the curves were found to be at
first convex to the base line and towards the end of the experi-
ment slightly concave, but in every case over a period of at least
two hours their progress was rectilinear. The inclination of this
part of the curve differed for each salt. I assumed that during
the rectilinear period the rate of rise in concentration would be
directly proportional to the velocity of diffusion of the salt. In
order to test the validity of this assumption I made experiments
with lithium, sodium and potassium chlorides, since the relative
rates of diffusion of these substances have been determined already
by physicists, using other methods}.
* A gelatine jelly of this strength has been shown by Hardy to have the struc-
ture of an open network.
+ Quoted in Handbuch der anorg. Chemie, 11. 1, Abegg u. Auerbach, 1908.
Also, Landolt-Bérnstein’s Tabellen, 1903.
+ I have unfortunately been unable to apply the method of calculation, since
worked out by Mr Hill, to these observations owing to the neglect of a simple
precaution in my first experiments. The solution was introduced at a temperature
25—2
Mr Mines, On the relative velocities of diffusion in
384
‘N 980:
= GE800:
(3
pue
66
(7
66
66
‘NI [- WoIyVaqueou0|D =0ZG00- JUeUITIedxe Jo Suruutseq ye woryN[os [QBN FO Aqtatonpuos oytoedg
ee Se
L010 | PLOTOO- GE100:
66600: | ¢810100- F6C100:
16600: | 996000: ZEZ100-
1300 | 688000: C9100:
10300: | ¢g1g000- 760100:
€100. | G8>L000: #0100:
9¢900- | 19000: 146000:
‘aaano jo qaed yysreayg {| 1800: ¢¢09000: 188000:
F1500 | FE000- 018000:
7700: | G6¢+000- ¢£1000:
TLE00: | GL82000: £99000:
¢0¢00- | OL1E000: | ¢z6c000:
9cc00- | ¢6rz000- | ogzc000-
TZ100- | O@81000: | ¢4cF000:
e100. | stztoo0- | 9862000:
71000. | 4610000 | 1¢¢¢000-
¢e000- 6g0000- | og1e000-
e1000- | 2LG10000: | Z16z000-
Gi PATO OMNCa TR. Np UU BOUTS ee
D901 peonpoiqUr pue LOVVM peaouory J a Sagi 661Z000
peel ae eae eS 53 aber
‘00 OT PUB EUTZLIES ‘o°0 G TIM TIPO
HWOMBIJUIONOD -
Se anE e2T S (2 = ) ¥y
66
OLF of LL O'1T
L6¥ Sl ~ 0¢ 01
IGG ol “001
1¢¢ o81 “Os
ggg SL 22.06
869 Ol 2088
919 6:1 OS
OS) Sl “OGL
r61 oS omens)
LLS aeT pen en0
016 Sil ~ Oo)
C801 81 OGG
CCCI ol: ST ~ (g
90FT o8l 0SiF
OZ9T Sl SOY
OF0G oS ~ 08'S
L06Z LSI ORS
O1GG Sl = (OS
OLS% oS OC
ate oe (79 Og ° I
GHEE o8l onl
GEG oS ‘urd GT ZI
red Sl “We GFT
SsuIyO UL
SONUE ISNT aL SGncinen oul y,
a
aqueous solution of rubidium and caesium chlorides. 385
One experiment may be quoted at length.
In this experiment there was a period of four hours, during
which the increase in concentration proceeded at a practically
uniform rate.
At 5.30 the concentration was °00303 Mol. NaCl.
At 9.30 29 ” 2 ‘0087 ” 2)
Thus in four hours the increase was ‘00567 or ‘001417 per
hour.
Experiments made in the same way with the other salts
yielded the following numbers. The observations are plotted in
fig. 2.
‘012 CsCl
ei | FRCL
‘Ol iG NaC
00
ib ot
2 0
Sb007
= +006
El -aps an, Lit
Ghoo4
hy-o03 WY,
F 002
S001 A
Hours ah oh J 4 Ss 6 i ig gq 10
Fig. 2.
Deci-normal Caesium chloride...... ‘0018 Mol. per hour
3 Rubidium chloride ... ‘001748 ,, ,, ,,
< Rotassrumuyenloride. 2. “0010 saa
x Sodium chloride ...... <OOUA rare ee
% Lithium chloride ...... 001165 _,, ps fe
Or taking the rate of diffusion of potassium chloride as unity,
and disregarding the last decimal place, we have
CsCl 1:05(5), RbCl 1:02(3), KCl 1-000, NaCl 0830, LiCl 0°68(4).
below that of the water bath and some few minutes must have elapsed before
18° was reached. The effect of this delay is to slightly displace the curve to the
right without affecting its form except at the very beginning. My calculations are
based entirely on the inclination of the curve during a period beginning three
or four hours after the experiment was started.
386 Mr Mines, On the relative velocities of diffusion, ete.
In the following table these results are compared with some
figures given by previous observers for the relative diffusivities of
potassium, s sodium and lithium chlorides.
CsCl RbCl KCl NaCl LiCl Observer
oe nt 1-0 8337 = Beilstein*, 1856
as = 1:0 ‘763 55 Schuhmeister7, 1879
= = 1-0 sad 674 | Longt, 1879
Zane = 1:0 805 “685 Oholm§, 1905
zat = 1:0 835 -— J. C. Graham||, 1905
— _ 1:0 ‘76 T17 =| J. C. Graham {, 1907
1:05(5) | 1:02(3) | 1:0 ‘830 ‘68(4) | Mines, 1910
It will be noticed that in the last two columns my numbers
fall within the limits of variation of those quoted above. This
fact I consider to justify the extension of the method to the study
of rubidium and caesium chlorides. In making these experiments
I aimed only at getting a rough comparison of the diffusion rates
of these substances, but I believe that the method might be used
to obtain values of considerable accuracy.
It would be easy to simplify the conditions by keeping one
end of the cylinder of jelly in contact with a dilute salt solution
renewed at frequent intervals and the other end in contact with
distilled water. It is obvious that the method is limited to those
electrolytes which are not hydrolysed in solution.
Conclusion. In dilute aqueous solution at 18° C. rubidium
chloride diffuses slightly faster than potassium chloride and
caesium chloride slightly faster than rubidium chloride.
The chlorides of the alkali metals show a rise in their rate of
diffusion which follows the same order as the increase in their
molecular weight and in the velocity of their kations.
My friend, Mr A. V. Hill, of Trinity College, has kindly indi-
cated a mathematical treatment of the subject in the following
note.
* Beilstein, Liebig’s Annalen, xcrx. 1856, p. 165.
+ Schuhmeister, Landolt-Bérnstein’s Tabellen, 1905.
+ Long, Annalen der Physik u. Chemie, rx. 1880, p. 613.
§ Oholm, Zeit. Physik. Chem. u. 1905, p. aU
| J. C. Graham, ibid. p. 257.
| Ibid. wrx. 1907, p. 91.
Mr Hill, Use of experimental method of preceding paper. 387
Note on the use of the experimental method described in the
preceding paper. By A. V. Hit, Scholar of Trinity College, and
George Henry Lewes Student.
ACDB is the tube containing the gelatine, which stretches
from AB to the bottom CD of the tube. Then the conditions
throughout the gelatine ACDB must be the same as if we had
double as much gelatine AHFB, and KCl (e.g.) solution at each
end. For in the first case the bottom of the tube hinders diffu-
sion across the plane AB: in the second case from considerations
of symmetry there can be no diffusion across the plane CD.
Gg and Hh are the platinum electrodes. AC =5- CE.
Let y be the concentration at any point P measured a distance
x along the tube.
Then we have the equaticn for the diffusion,
ON ae Ody
ot t Ou?
if ¢ is the time.
A solution of this equation which satisfies all conditions is
Y=Yot = Lp sin —.
For (1) at x=0, y= y, the constant concentration of KCl.
(2) ate — Onn.
(3) y can be made equal to 0 at ¢=0.
We have at t=0
2 5. Pusde
0=y+>A,sin —.
1 a
388 Mr Hill, Note on the use of the experimental
Multiplying by sin — and integrating between the limits
0 and a, we have
a a a
Wane a rune
0=y%| sin +A,[ sin? ——
=O a 0
ee cos me — cos 0|+ A
ro | a
9?
when 7 is even A, =0,
when r is odd Pete tet I Aa
Qa rT TT
% 1 ~, ea. (Qn—1) 0H
oe —
Hence we may draw two conclusions.
(1) To make results with the instrument easily and
directly comparable it is advisable to keep 5° the amount of
gelatine used, the same in different experiments.
(2) With this condition if kt in one experiment =k’t’ in
another, the concentration at any point P is the same in either
experiment. Hence if we compare the times at which equal
concentrations are reached these must be inversely proportional
to the diffusion constants of the two salts. With a series of
observations therefore at equal intervals of time the concentrations
can be plotted and the curve compared with the standard curve
obtained for one salt whose diffusion constant is known. The
ratio of the times to equal concentrations can be compared at
several points of the curve: this ratio should be found nearly
constant, and its mean value for several concentrations will give
the ratio of the diffusion constants very accurately.
If we suppose the conductivity to be directly proportional to
the amount of salt between the two electrodes we shall have the
conductivity
q co 1 4 Coens . (2n—1) re
A= py | Fool ee sin SUT a,
where p and q are the values of « for the ends g, h, and G, H, of
the electrodes, and yw is some constant, depending on the conduc-
tivity and the size of the plates.
e i i (2n — 1) wp
A= LY a —P)— 403 aye & eo
eee —
a
method described in the preceding paper. 389
From a measurement of the constants a direct estimation
might be made of the diffusion constant of any one salt.
By plotting the logarithms of the time and the logarithms of
the conductivities the curves for two different salts will be found
to be the same, though situated at a different position. The
amount that one must be displaced along the axis of time in
order to coincide with the other gives the ratio of the diffusion
constants: the amount of displacement along the axis of con-
ductivity gives the ratio of the conductivities,
390 Mr Arber, A note on some fossil
A note on some fossil plants from Newfoundland. By EH. A.
NEWELL ARBER, M.A., F.LS., F.G.S., Trinity College.
[Read 7 February 1910. ]
The present preliminary note is concerned with two fossil
plants, not hitherto recorded from Newfoundland. Our know-
ledge of the plant-remains from this region is at present very
slight, and is confined to a few Upper Carboniferous species de-
scribed by Dawson*. The impressions, discussed here, occur in
a sandy shale exposed in the bed of the Shenanditti River, on
the west side of Red Indian Lake in the interior of Newfoundland.
Text-fig. 1. Sphenophyllum tenerrimum, Stur.
Two leaf whorls, each composed of six or more repeatedly dichotomous, narrow
segments. No. 269 Sedgwick Museum, Camb. x2.
The specimens, which are well preserved, were presented to the
Sedgwick Museum by the generosity of Mr Rowland Feilding in
1908.
There are only two species to be recorded and these were
associated. One of them is a Sphenophyllum, which appears to
* Dawson, Rep. Foss. Plants, Lower Carbon. and Millstone Grit, Canada (Geol.
Surv. Canada, 1873), pp. 29, 32, 34.
plants from Newfoundland. 391
be very closely similar to, if not identical with, Sphenophyllum
tenerrimum, Stur*, known from the Lower Carboniferous rocks of
Silesia. Both leaf whorls and stem impressions are represented.
Two of the former are seen in text-fig. 1, magnified twice.
The whorl consists of six or more dichotomously branched
narrow segments. Jn some cases the leaves dichotomise twice,
in others, three times. The first dichotomy may take place at
the base of the leaf, or a little above the base.
Sphenophylls possessing this reduced and repeatedly forked
type of foliage are known both from the Lower and Upper
Carboniferous. In some Coal measure species, both normal wedge-
shaped leaves and leaves with reduced forked segments may
occur on the same stem. In the case of S. tenerrimum, Stur,
however, as in the present specimen, there are no indications
that would lead one to suppose that the plant was heterophyllous.
With the Newfoundland specimens we may also compare the
Sphenophyllum subtenerrimum of Nathorstt from the Upper
Devonian rocks of Bear Island in the Arctic regions. Here how-
ever the leaf whorls appear to be smaller in sizef, and the leaf
segments even more delicate.
Impressions of stems of Sphenophyllum, possibly belonging to
the same species as the leaves described above, are also associated.
One of these is shown in text-fig. 2, where two somewhat tumid
nodes are seen, with which fragments of leaves, which lie at right
angles to the plane of the stem as seen in this specimen, appear
to be still in continuity. The internodes exhibit two rather
sharp longitudinal ridges, which are fairly distant from one
another.
This stem appears to be somewhat stouter, and the internodes
more elongated, than the stem specimens of S. subtenerrumum
figured by Nathorst.
The other plant collected from the Shenanditti River is of
special interest for it appears to be new to science, at least
specifically, if not generically. In Mr Feilding’s collection, several
examples of a large fan-shaped leaf are more or less completely
preserved. These leaves often exceed 14 cm. in length and
breadth. The nerves radiate from the base and are numerous,
dichotomising here and there in the broader portion of the leaf.
All the examples are detached. At the base the leaf narrows
somewhat rapidly and appears to have been sessile.
These leaves recall some species of the rare and little known
genus Psygmophyllum, Schimper, more closely than any of the
* Stur (Culm Flora, Part 11.), Abhandl. k. k. Geol. Reichsanst, Wien, Vol. vii.
1877, p. 108, pl. vir. (xx1v.), figs. 1—14.
+ Nathorst, K. Svenska Vetenskaps-Akad. Handl., Vol. xxxv1. No. 3, 1902, p. 23,
pl. 2 (figs. 14—17), pl. 3 (figs. 7, 8), pl. 4 (figs. 14—-23), pl. 5 (fig. 5).
+ Ibid., pl. 4 (figs. 22, 23).
392 Mr Arber, A note on some fossil plants, ete.
other fossils recorded from the Palaeozoic rocks. Psygmophyllum
as at present constituted is probably a composite genus. At a
future opportunity it 1s proposed, when describing these fossils
more fully, to review the present position of our knowledge of
the plants which have at one time or another been assigned to
it. The present preliminary note may serve to record the dis-
covery of these interesting fossils in a region which hitherto has
remained almost a terra incognita in a palaeobotanical sense.
Text-fig. 2. Sphenophyllum, sp.
A stem showing two nodes, to which fragments of leaves are attached.
No. 339 Sedgwick Museum, Camb. x1}.
The only evidence of the age of the rocks from which these
specimens were obtained is that presented by the fossils them-
selves, From the occurrence of Sphenophyllum tenerrimum,
Stur, one would suppose that the period is either Lower Carboni-
ferous or Upper Devonian, the former being more probable.
Mrs Arber, A note on Cardiocarpon compressum, Will. 393
A note on Cardiocarpon compressum, Will. By Mrs E. A.
NewetL ArsBeER, D.Sc, Newnham College. (Communicated by
Mr E. A. Newell Arber.)
[Read 7 February 1910. |
In 1877 Williamson * described and figured a small unattached
winged seed showing binary symmetry, from the Lower Coal
Measure nodules of Oldham, which he referred to Brongniart’st
genus Cardiocarpon. On account of its flattened form he gave it
the specific name compressum. Other Cardiocarpons had previously
been described from the British Coal Measures, but only their
external appearance was known, whereas in the new species the
internal structure was preserved. Williamson figured sections cut
from three specimens. The most characteristic feature of the seed
was that the testa was divisible into two very distinct layers,—
an exotesta of coarse parenchyma, and an endotesta of much
smaller cells. No further description of the internal structure of
Cardiocarpon compressum, or of that of any other seed showing
bilateral symmetry from the British palaeozoic rocks, has been
published since Williamson’s time. The main interest of the
genus Cardiocarpon lies in the great probability that it repre-
sents the seeds of Cordaitest. The possibility is not however
excluded, that seeds of this type were borne by Pteridosperms,
for seeds of binary symmetry have been found attached to fronds
of Aneimites§ and Pecopterts Pluckeneti||. The following note
is based on material collected by Prof. F. W. Oliver, Dr D. H.
Scott, and Prof. Weiss, and generously made over to the present
writer for examination. The material consists entirely of sections
of unattached seeds occurring in the “coal balls.” The same
seed is seldom met with in more than one section.
The contrast between exotesta and endotesta already men-
tioned affords the readiest means of identifying Cardiocarpon
compressum in microscopic section. There. is sufficient variation
among the specimens, both in dimensions and structure, to suggest
- that Cardiocarpon compressum, instead of being a single species,
may possibly represent an assemblage of seeds belonging to closely
* W. C. Williamson, ‘‘On the Organisation of the Fossil Plants of the Coal-
measures,” Pt. vit., Phil. Trans. Roy. Soc. Vol. cuxvi. Pt. 1. p. 213.
+ A. Brongniart, Prodrome d’une histoire des végétaux fossiles, Paris, 1828.
+ F. C. Grand’-Eury, Mémoire sur la Flore Carbonifére du Département de la
Loire, 1877, p. 233.
§ David White, ‘The Seeds of Anecimites,” Smithsonian Miscellaneous Collec-
tion, Vol. xuvi1. 1905, p. 322.
|| F. C. Grand’-Eury, ‘‘ Sur les graines trouvées attachées au Pecopteris Plucke-
neti, Schlot,” Comptes Rendus, t. cxu, 1905, p. 920.
394 Mrs Arber, A note on Cardiocarpon compressum, Will.
allied plants. The sclerotesta or shell consisted of two flattened
valves, pointed above and broadest near the base. In both length
and breadth these valves slightly exceeded half a centimetre.
In well preserved specimens the shell is enclosed in a delicate
sarcotesta forming a thin layer over the surface of the valves,
and at their lateral edges extending beyond them as a wing
lying in the plane of flattening. The wing appears to have
terminated in a short downward prolongation on each side of
the hilum, giving the seed a remote resemblance to a mitre. It
should be mentioned that Williamson took a different view of
the structure, and figures the sarcotesta as continuous round the
base of the seed.
Williamson’s preparations did not admit of his observing the
vascular system, which is of some interest. The main supply
bundle enters the hilum and expands into a funnel-shaped mass
below the nucellus. Here it gives off two opposite branches in
the plane of flattening of the seed. These branches are at first
horizontal, but they soon bend downwards and outwards, travers-
ing the shell in an oblique direction. On emerging into the
sarcotesta they curve upwards and run to the micropyle following
the slight groove at the junction of the valves. The base of the
nucellus is supplied by tracheides given off from the expanded
end of the central bundle above its two main branches. I have
not been able definitely to satisfy myself as to whether a nucellar
vascular system arises from this basal tracheal plate.
Inside the shell there are indications of an “inner flesh,”
which is however seldom preserved. The nucellus seems to have
been free from the integument from the base upwards. The
megaspore is usually empty and contracted, but in one case a
tissue occurs within it which may be a prothallus.
I have provisionally adopted Williamson’s name for this seed,
Cardiocarpon compressum, but it is doubtful whether it should
be permanently retained. The question of nomenclature, which
presents some difficulties in this case, will be discussed at length
in a detailed paper which I hope to publish shortly.
Mr Gordon, On a new species of Physostoma, etc. 395
On a new species of Physostoma from the Lower Carboniferous
Rocks of Pettycur (Fife). By W.'T. Gorpon, M.A., B.Se., Falconer
Fellow of Edinburgh University, and Advanced Student Exhibi-
tioner of Emmanuel College. (Communicated by Mr E. A. Newell
Arber.)
[Read 7 February 1910.]
Among the rarer petrifactions of plant-remains occurring in
the Calciferous Sandstone Rocks at Pettycur are seed-like bodies
of various kinds. Perhaps the commonest example is Lepido-
carpon wildianum, Scott*, while occasionally the pteridospermous
fructification—Conostoma ovale, Williamson*+, is also met with.
Under the name Conostoma intermediat Williamson also placed
what are probably elongated specimens of C. ovale. These two
seed bodies are very distinct, for Conostoma has a funnel-like
micropyle, whereas Lepidocarpon has no true micropyle. The
megaspore in the latter was exposed to the exterior by means
of a slit-like aperture between two enveloping outgrowths from
the sporophyll.
Last year Prof. Oliver§ published his work on Physostoma
elegans, and showed that in that genus the apex of the seed
consisted of closely adpressed, free, tentacular processes; the
micropyle was thus capable of great enlargement.
In the same paper he refers to C. ovale as being probably the
seed of Heterangium grievw, Williamson. The only evidence
however is association. Recently, while examining a new species
of Heterangium from Pettycur, I discovered several specimens of
C. ovale, and among them what appears to be a new and distinct
seed. The specimen had been cut through in an oblique tan-
gential direction, but by careful preparation I was able to get
one of the sections more nearly radial. One section is through
the micropylar orifice and the other passes through the chalaza.
GENERAL STRUCTURE.
The seed is radially symmetrical and is considerably larger
than C. ovale. The following table gives the dimensions of the
new seed and those of C. ovale.
* Scott, Phil. Trans. Roy. Soc. B. Vol. cxctv. 1901, p. 291.
+ Williamson, Ibid. Vol. cuxvit. 1877, p. 243. t Ibid. p. 246.
§ Oliver, Ann. Bot. Vol. xx111. 1909, p. 73.
396 Mr Gordon, On a new species of Physostoma
New Seed (Physostoma) Conostoma ovale
engthiy seer 3°8 mm. 3°2 mm.) Average of
5 radial
Breadth ...... 3°3 mm. 2:1 mm.) sections
The length of the new seed is probably greater than indicated,
since both sections are oblique, and 4 mm. would probably not
be an excessive estimate of the true length. The breadth is also
considerable, and indeed the almost globular shape of the seed
is striking. The base is rather flat and the micropyle is not
prominent.
The seed at the apex shows a number of tentacular processes
and the outer surface is studded with small peg-like hairs. The
occurrence of these characters warrants its inclusion in the genus
Physostoma as lately defined by Oliver.
All the Pettycur seeds I have examined are poorly petrified,
and this new one is no exception. The description must there-
fore be meagre.
The nucellus is capped by the pollen chamber but there is
no dome-like projection of the nucellar apex into the cavity of
the pollen chamber. Indeed, in that region the seed is quite like
Conostoma and not Physostoma. Outside the membrane of the
nucellus the tissues are all decayed; only the vascular bundles
remain. Near the chalaza however and in one of the apical
processes a slight amount of delicate parenchymatous tissue
can be observed, but it is too fragmentary to warrant detailed
description.
The outer layers of the integument have all decayed into a
structureless dark zone about ‘2 mm. thick. There are no ribs
on the outside of the seed, but the whole periphery is covered
with small dark dots. These lie in a zone concentric with the
seed and about ‘1 mm. outside. Near the micropyle these dots
are seen to occupy the ends of short finger-like cells which clothe
the seed externally. They are quite similar to the peg-cells of
Lagenostoma and may be equivalent to the hairs on Physostoma
elegans. In this new specimen the hairs are equal in length all
over the surface. In outline the hairs are short and have rounded
ends.
The most interesting part of the seed, however, is the micro-
pylar end. There we find a pollen chamber in the usual position
at the apex of the nucellus. The orifice of this chamber is not
visible owing to the obliquity of the section and it is uncertain
whether there was a funnel-shaped aperture as in Physostoma
from the Lower Carboniferous Rocks of Pettycur (Fife). 397
elegans or a depressed aperture as in Conostoma ovale. The
micropyle which lies immediately over the opening of the pollen
chamber is also cut tangentially and in the most radial section
is clearly bounded by three separate tentacle-like processes.
The chalazal end is also interesting from the fact that the
bundles enter the seed independently as in Physostoma.
This new species of Physostoma, which is more ancient than
P. elegans recently described by Professor Oliver, combines
with its Physostoma characters, others which are typical of the
genus Lagenostoma. The tentacular processes at the apex
suggest affinities with Lagenostoma in that they are less di-
vergent than in Physostoma (ie. they clasp the pollen chamber
more tightly), and thus the seed has the whole apex flattened
as in Lagenostoma. On the other hand the structure of the
pollen chamber, so far as is known, is quite unlike that of
Lagenostoma. The seed may however eventually require to be
placed in a new genus.
In conclusion I have to thank my supervisor Mr Arber for
his kindly criticism and advice.
VOL. XV. PT. V. 26
398 Mr Gordon, On the relation between the
On the relation between the fossil Osmundaceae and the
Zygopterideae. By W. T. Gorpon, M.A., B.Sc. (Edin.), Falconer
Fellow of Edinburgh University, and Advanced Student Exhi-
bitioner of Emmanuel College. (Communicated by Mr E. A.
Newell Arber.)
[Read 7 February 1910.]
The structure of the axis in the living Osmundaceae has given
rise to two main contentions as to the evolutionary position of the
group. The axis is regarded by Jeffrey* and Faull} as reduced
trom a more complex dictyostelic ancestor, and by Boodlet, Seward
and Ford§, Chandler||, Tansley{, and Kidston and Gwynne-
Vaughan ** as the latest development in an ascending series from
a protostelic ancestor.
This latter view is supported by the ontogenetic development
of living species and, now that Kidston and Gwynne-Vaughan
have completed their studies on the fossil representatives, by the
phyllogeny of the group as well.
The present living genera may be placed in two categories.
Osmunda regalis may be taken as one extreme type where the
leaf gaps are long and a cross-section of the stem consequently
showing a ring of several xylem strands. In cases where the
leaf gap is short as in Todea barbara and T. superba a cross-section
shows the xylem as a much more continuous ring. This may be
looked upon as the other extreme.
The stems of the most recent fossil representatives of the
Osmundaceae conform to these two extremes. Even Osmundites
Skidegatensis, Penhallow, is of the Osmunda regalis type, though
it may be regarded as an even more extreme example. (This
species seems to lend colour to Jeffrey’s reduction theory, but
the weight of the other evidence completely overrules this
single exception.) The tertiary species Osmundites schemnicensis
(Pettko) and O. Dowkeri, Carruthers, resemble Osmunda regalis,
and so does the Jurassic form O. Gibbiana, Kidston and Gwynne-
Vaughan. O. Dunlopi, Kidston and Gwynne-Vaughan, another
species from the Jurassic, has a xylem ring which is almost later-
Jeffrey, Phil. Trans. Roy. Soc. Vol. cxcv. 1902, p. 127.
Faull, Bot. Gaz. Vol. xxxi1. 1901, p. 418.
Boodle, Ann. Bot. Vol. xvit. 1903, p. 515.
Seward and Ford, Trans. Linn. Soc. London, Series 2, Vol. v1. 1902, p. 254.
Chandler, Ibid. Vol. xtx. 1905, p. 406.
Tansley, New Phytologist, Reprint No. 2, 1908.
Kidston and Gwynne-Vaughan, Trans. Roy. Soc. Edinburgh, Vol. xuy. Pt. 3,
eae p. 759; ibid. Vol. xuvi. Pt. 2, 1908, p. 213; ibid. Vol, xuvi. Pt. 3, 1909,
p. 651,
Mtr *
—_—
He
fossil Osmundaceae and the Zygopterideae. 399
ally continuous, i.e. the leaf trace departs typically in a protostelic
manner. ‘This also occurs occasionally in 7. superba, so that
QO. Dunlopi may be considered as pointing to Todea rather than
to Osmunda regalis.
In the Jurassic period therefore forms existed which were
practically as divergent as the living ones are. The only differ-
ence is shown in O. Dunlopi, where the leaf trace is typically
protostelic in its departure. The type of this last species is
still further accentuated in Upper Permian times in the case
of Zalesskya, Kichwald, and Thamnopteris, Kichwald. Both of the
last-named genera have not only the xylem ring continuous
laterally but they have no central pith. The central tissue of
the stem consists of short, reticulated tracheides.
In the Permo-Carboniferous genus Grammatopteris Kidston
and Gwynne-Vaughan see the earliest example of a plant with
Osmundaceous affinities, and here we find a perfect protostele
with only one type of xylem tissue. This genus however is still
imperfectly known.
The leaf trace in the fossil Osmundaceae also shows a very
distinct passage from exarchy to endarchy, and from protostelic
departure to cases where leaf gaps occur. The most interesting
example is probably Thammnopteris schlechtendali, since in it we
occasionally find leaf traces with double mesarch protoxylem
groups. Even where such double protoxylems are found the
trace develops normally afterwards.
Turning now to Zygopterid alliance, we find that the youngest
known representative is Asterochloena Corda ranging to the
Devonian. The stem xylem in this genus is stellate with exceed-
ingly long rays and a pith is always present. The trace has two
mesarch protoxylem groups. In the Permo-Carboniferous of Autun
Z. Brongniarti, Renault, occurs. The stele in this case has almost
circular xylem with a true pith and a system of internal tracheides
in that pith. The outer xylem ring is interrupted by the depart-
ing leaf traces. Z. Grayi, Williamson, from the Coal Measures, has
a stellate xylem but the rays are very short. A central pith and
system of internal tracheides are present.
Corresponding to Z. Brongniarti in the Permo-Carboniferous we
have Z. Corrugata, Williamson, in the Coal Measures. The organisa-
tion of this stem is quite similar to Z. Grayz, but in outline it has
become more circular. The differences between the outlines in
these two species seems to be correlated with the greater length of
the internodes. The lately discovered stem of Diplolabio Romeri
Solms from Lower Carboniferous rocks exhibits the most primitive
type of zygopterid stem so far known. The stem as seen in trans-
verse section, in cases where no petioles are departing would be
classed as a Botryopterid. The wood is solid and of two kinds,
26—2
400 Mr Gordon, On the relation between the fossil, ete.
forming an inner and an outer zone. The thickenings on all the
elements are reticulate, except the protoxylem groups, where they
are scalariform. The leaf trace departs in a protostelic manner,
and has two immersed protoxylem groups.
Among the Botryopterideae, B. cylindrica (Williamson), from
the Coal Measures, represents probably the highest known type
of development. Here the inner elements of the stem xylem
are smaller than those of the outer xylem. In B. antiqua,
Kidston, there is only one type of xylem element. In the last
species I have been able to show that the leaf trace is at first
mesarch.
The thickenings on the xylem elements in these three groups
are interesting. In the Osmundaceae we get a series from
multiseriate pits through scalariform to reticulate thickenings.
Reticulate tracheides only occur in the archaic forms Zalesskya
and Thamnopteris and then only in the inner wood. The last-
mentioned type of thickening must therefore be considered the
most primitive. Among the Zygopterideae we find a similar
series from scalariform to reticulate (in D. Rémeri); in the
Botryopterideae from scalariform to reticulate.
Except for the multiseriate pits on the external xylem elements
Thamnopteris could not be distinguished from the zygopterid
D. Rémeri on stem structure. The leaf trace has of course typi-
cally only one protoxylem group, but occasionally examples with
two are found. This feature may be considered as being probably
primitive since the double group ultimately functions as if it
were a single one. In D. Romeri the leaf trace has typically two
protoxylems and I have never observed either more or fewer than
that number. It is clear then that at first sight in their most
primitive representatives the two groups of the Osmundaceae and
the Zygopterideae cannot be distinguished in their anatomical
features. The two groups show exactly parallel development
from the two primitive types just cited, and it thus seems prob-
able that they have diverged from a common stock. The
geological position of the various representatives of these groups
points to the conclusion that the Zygopterideae diverged from
the parent stock before the Osmundaceae did; and the greater
suitability of the latter group for present conditions of growth
has allowed it to persist after the Zygopterideae had perished.
I desire to express my indebtedness to Mr E. A. Newell Arber,
under whose supervision my work is being carried on, for his
criticism and advice.
Mr Vernon, On the occurrence of Schizoneura paradoxa, etc. 401
On the occurrence of Schizoneura paradoxa, Schimper and
Mougeot, in the Bunter of Nottingham. By R. D. VERNON,
B.Sc., 1851 Exhibition Research Scholar, and Advanced Student
Exhibitioner of Emmanuel College. (Communicated by Mr E. A.
Newell Arber.)
[Read 7 February 1910.]
From the English Trias recorded fossils are extremely rare and
appear to be restricted to the Upper or Keuper division. The
Lower Trias has hitherto yielded, so far as I am aware, only
derived fossils which are contained in the constituent pebbles of
the middle or “Pebble Bed” subdivision of the Bunter. The
discovery of fossil plant-remains from the Bunter of Nottingham
is thus of some general interest, for they appear to be the first
contemporaneous fossils from the Bunter of England. Equise-
taceous pith casts of doubtful attribution were the first specimens
obtained; they were provisionally determined as Hquisetites sp.,
and are so mentioned in the recently published Geological Survey
Memoir on the Nottingham district*. Subsequent collecting has
yielded a large number of fragmentary plant-remains including
not only pith casts but also leaves, stems, and roots; occasionally
specimens are found showing two or more organs still in organic
connection. All the fossils may be referred to Schizoneura para-
doxa, 8. and M., and there is reason to believe that they originally
grew on the spot where they now occur.
The fossiliferous section is a now disused sand-pit at the foot
of Colwick Wood, by the west side of the Great Northern Rail-
way bridge over Colwick Road, Nottingham. The section shows
the regularly-bedded marls and thick sandstones of the Lower
Keuper (Waterstones) with a thin conglomerate at the base,
resting on a sharply marked and eroded surface of the Bunter
Pebble Beds, which here consist of strongly current-bedded pebbly
sandstones containing nodules and lenticular beds of red marl.
It is from the uppermost lenticular bed of marl in the Bunter,
a few feet below the basal conglomerate of the Keuper, that
all the plants have been collected. The section is figured and
described at length in the Geological Survey Memoir on the
district F.
* “ Geol. country between Newark and Nottingham” (Mem. Geol. Surv.), 1908,
p- 42.
+ Ibid. p. 37.
402 Mr Vernon, On the occurrence of Schizoneura paradoxa,
EQUISETALES.
Schizoneura paradoxa, Schimper and Mougeot, 1844.
1828. Calamites arenaceus, Brongniart, Hist. véget. foss. Pl. XXII.
fig. 1.
1844, eae paradoxa, Schimper and Mougeot, Monog.
Plant. foss. Vosges, p. 48, Pls. XIV. XV. XVI.
1844. Calamites arenaceus, ibid. p. 57, Pl. xxvii. fig. 2.
1844. Calamites mougeoti, ibid. p. 58, Pl. xxix. figs. 1, 2, 3.
1870. Hquisetites mougeott, Schimper, Traté, p. 279, Pl. xu.
fig. 4.
1907. Hiiacheee arenaceus, Arber in Wills’ Geol. Mag. Dee. 5,
Vol. Iv. p. 32.
1910. Schizoneura paradoxa, Wills, Proc. Geol. Assoc. Vol. XX1.
Part 5, p. 272.
Localities. Voltziensandstemm (Upper Bunter) of the Vosges.
Lettenkohle (top of Muschelkalk) at Neuewelt, Basle, Switzerland.
Lower Keuper Sandstone at Bromsgrove and other places in
Worcestershire. Bunter Pebble Beds of Nottingham.
Diagnosis. From a study of the specimens in the Strassburg
Museum, including the original material of Schimper and Mougeot,
and of the Worcestershire specimens, described in his recent
paper, Wills* has drawn up the following diagnosis :
“Large plants, stems up to two inches in diameter, stems
divided into nodes and internodes, internodes long, larger stems
either ridged or smooth, pith either wholly or partially hollow;
branches borne in whorls at the nodes, external surface of branches
usually smooth or nearly smooth; leaves long and _ strap-like,
borne in whorls at the nodes, leaves united either into a sheath
or into sheath segments or free to their bases, border of leaves
smooth, median part of leaves with fine close-set parallel nerves,
cone probably with peltate areas on external surface, roots arising
from the nodes, roots small and repeatedly branched.”
Schizoneura must still be regarded as an imperfectly defined
genus. Of the cone our knowledge is of the slightest, and of the
internal anatomy of the plant we are quite ignorant. The frag-
mentary nature of the stem casts renders identification in many
cases doubtful or even impossible. Ridged and grooved casts are
of common occurrence, some of these may represent the external
surface of the stem, or they may be the impressions of the external
surface more or less modified by the internal structure, as pointed
out by Wills; more usually they are interpreted as pith casts.
Such fragmentary pith casts cannot be generically identified,
they may belong to one of several members of the Equisetaceae.
* Wills, ‘‘ The Fossiliferous Lower Keuper Rocks of Worcestershire,” Proc.
Geol. Assoc. Vol. xx1. 1910, Pt. 5, p. 272.
Schimper and Mougeot, in the Bunter of Nottingham. 403
A further source of possible error depends on the fact that
this diagnosis is necessarily founded on fragmentary material
from various localities occurring in association with remains of
other plants. This latter objection does not apply to the fossils
described below since they appear to belong wholly to one species
and are not associated with any other plant-remains.
DESCRIPTION OF THE SPECIMENS.
Detached leaves. These are fragments of long, narrow, deli-
cate, grass-like leaves, usually found detached but more rarely
occurring in organic connection with a stem. They have smooth
entire margins with a median group of exceedingly fine parallel
nerves.
One example has four and another has six leaves, in each case
the margins of the leaves are arranged parallel to one another.
These specimens may be regarded as portions of sheath-segments
composed of several leaves, originally united by their smooth
margins along the commissural lines. By splitting along these
lines the leaves have, in some cases, become either partially or
wholly free. :
Leafy shoot. A cast of the external surface of a small stem
about ‘5 cm. in diameter with a smooth, irregularly wrinkled
surface, bears a node from which arise four or more leaves forming
a leaf-sheath. Only the basal portions of the leaves are preserved,
and the clasping nature of the leaf-sheath cannot be made out
because the specimen has been flattened by crushing.
Leafless stems. The material furnishes at least four kinds of
casts and impressions of leafless stems:
(a) The first type are characterised by a smooth, irregularly
wrinkled surface and distinctly swollen nodes.
In these features they agree exactly with casts of the external
surface of leaf-bearing stems.
(b) Occasionally a cast of the above type is folded into some-
what broad furrows and narrow ridges.
A similar structure occurring in casts of Schizonewra meriant
was explained by Schimper * as due to an accident of preservation.
(c) Several casts of portions of large stems differ from type
(a) only in the fact that their smooth surfaces are faintly but
regularly ridged and grooved. They may be regarded as either
the casts of the external surface of large, faintly-ribbed stems,
or the ribbing may be ascribed to the action of the internal
structure.
(d) What appears to be a more internal cast than the above
has internodes strongly marked with longitudinal ridges and
* Schimper, Traité de Palaeontologie Végétale, 1869, p. 282.
404 Mr Vernon, On the occurrence of Schizoneura paradoxa,
grooves, which, in the best preserved specimens, appear to be
continuous at the node. The specimens vary greatly in size, in
the coarseness and fineness of the ribbing, and in the character
of the ribs, which are generally broad and nearly flat-topped.
Reversed casts also occur in which the ridges are represented by
grooves, causing the true grooves to stand out as narrow ridges,
whilst the nodal constriction is now represented by an upstanding
ridge. These specimens are undoubtedly Equisetaceous pith
casts, which, by themselves, cannot be generically identified.
Branching. Certain specimens of the (d) type appear to be
casts of the pith cavity of large branches. They are gradually
contracted towards the base of the branch, just as is the case
with the medullary casts of Calamites. Large scars which occur
on the nodes of other casts of the (d) type may thus be inter-
preted as branch scars.
Nodal Diaphragms. Some interesting examples of nodal
diaphragms have been collected. One specimen of the exterior
portion of a stem with a node shows a diaphragm displaced by
crushing, somewhat in the manner so often found in Hquisetites
lateralis. Other specimens have a smooth, central concave portion,
bearing at the node a number of long, stout, narrow, spoke-like
structures which appear to be branches.
Many of the diaphragms, apparently belonging to the under-
ground stem, are still in the position of growth and appear to
have suffered hardly any distortion. Radiating from the edge
of the node are four, five, sometimes six, roots which at first
are confined to one plane; they bear numerous branching
rootlets which ramify in all directions. One specimen of a small
diaphragin, only 12 mm. in diameter, has, attached to the node,
four roots which bear numerous rootlets. Another broader, thicker,
more woody looking structure with a smooth surface is also borne
at the node; this appendage is quite different from, and very
much larger than the associated roots; it appears to be a portion
of a stem.
Roots. In addition to the roots described above which are
found still attached to the node, there are numerous examples
of detached fragmentary roots and rootlets, which show the same
characters. All possess a smooth, irregularly wrinkled, or finely
reticulated, external surface. Occupying the central axis of the
root in several specimens is a stout central structure which
probably represents the stele, its surface bears the imprint of
longitudinal and transverse lines giving an appearance strikingly
suggestive of cell structure.
The rootlets differ from the roots merely in size; the angle
they make with the root is sometimes 60° but usually 90°.
Schimper and Mougeot, in the Bunter of Nottingham. 405
Conclusion.
The fossils indicate a large plant with smooth stems at least
three inches in diameter. Only the smaller stems appear to have
borne leaves, which were at first united by their margins to form
leaf segments or leaf sheaths. Later the leaves became more or
less free to their bases by splitting along the commissural lines.
The upper portion of the stem bore whorls of branches at the
nodes, whilst the underground stem gave off numerous slender,
probably adventitious, roots ending in branching rootlets.
The vegetative organs of this plant are so similar to those of
_ the Keuper specimens of Schizoneura paradoxa, 8. and M., de-
scribed by Wills, that they may be regarded as the same species.
At the same time a few minor differences are noticeable. The
pith casts differ amongst themselves, and also from the Keuper
specimens, in size, and in the relative coarseness and fineness of
the ribbing; such variations may be expected to occur even in
different parts of the same plant.
Whilst the Keuper specimens of the root usually make an
angle of 60° with the rootlets, in the Bunter plant this angle is
nearly always 90°.
From the puckering of the leaves in the Keuper fossils Wills
inferred that those organs were thick structures; but the leaves of
the Bunter were undoubtedly thin and delicate.
In conclusion it may be remarked that this discovery of the
first evidence of contemporary life in the Bunter rocks of England
is not merely an interesting fact. The occurrence of the same
species of land plant in both the Lower Keuper and the Bunter
is of importance as evidence that the unconformity between these
two divisions of the Trias in the Midlands is probably not an in-
dication of a long lapse of time. It further suggests that the
physical conditions which prevailed during these two periods were
not very diverse.
406 Mr Wills, Notes on the genus Schizoneura,
Notes on the genus Schizoneura, Schimper and Mougeot. By
L. J. Wits, M.A., F.G.S., Fellow of King’s College. (Communi-
cated by Mr HE. A. Newell Arber.)
[Read 7 February 1910.]
The genus Schzonewra though of widespread occurrence is
still very imperfectly known. It was founded by the eminent
French palaeobotanists, Schimper and Mougeot, in 1844*, on speci-
mens from the Upper Bunter (Voltzien-sandstein) of the Vosges
Mountains, which they described as S. paradowa. Their definition
is somewhat loose, but its essential points are that the plant is of
an Equisetaceous nature, with stem divided into rather long
internodes; the leaves which are borne in whorls at the nodes
are at first united into a leaf-sheath. This later splits along
commissural lines into sheath-segments or into individual leaves.
Though various species have since been described from diffe-
rent horizons and countries, little has been added to our knowledge
of the structure of this plant since 1844. Recently I have had
the good fortune to collect abundant material from the English
Lower Keuper of Bromsgrove in Worcestershire, which in some
ways supplements our knowledge of the species S. paradoxa. It
may be of interest to point out some details of the nature and
structure of Schizonewra as exemplified by this, the original,
species. We may then be in a more advantageous position to
answer the question, whether the name Schizoneura has been
applied to plants genetically distinct or the reverse.
I have, however, described the Bromsgrove material in some
detail elsewhere+. Accordingly, I propose at present to mention
only the chief points of interest displayed by this plant. :
There is little doubt that S. paradoxa and possibly all the ~
other species, were lovers of moist spots and, in fact, probably
grew actually in the water; for we find at Bromsgrove rootlets
and stems still apparently in their position of growth. A similar
mode of occurrence has been noticed by other observers}. . Schizo-
neura paradoxa may well have reached a considerable height, for
stems up to about 2” in diameter and several feet in length have
been discovered.
Leafy branches are the best known portions of this plant.
The external surface of the smaller stems was probably smooth,
while the larger ones may have been slightly ribbed. The leaves
usually number seven. So far they have never been observed
* Schimper and Mougeot, Monographie des Plantes fossiles du Grés bigarré de
la chaine des Vosges, Leipzig, 1844.
+ Wills, L. J., Proc. Geol. Assoc. Vol. xxi. 1910, p. 271.
+ e.g. Rogers, A. W., and Seward, A. C.; see Seward, Quart. Journ. Geol. Soc.
Vol. uxtv. 1908, p. 89.
Schimper and Mougeot. 407
entirely united into a sheath, yet sheath-segments with varying
numbers of leaves are found. On the other hand, the leaves are
occasionally free to their bases. They are strap-like structures,
with smooth margins and a bundle of fine parallel nerves down
the centre.
The stems from which the leaves had fallen previous to pre-
servation are of various types. They are known from impressions
and casts. The external surface may have been smooth or possibly
finely ribbed. The internal casts or impressions are finely ribbed.
There are, however, two types of these, and their interpretation
must remain ambiguous until we learn something from petri-
factions about the internal anatomy of these Mesozoic Equisetales.
We may, nevertheless, note that the ribbing appears to be coarser
in the lower parts of the stem.
On certain of the ribbed internal casts there are at the nodes
two kinds of prints:—the larger lie just above the nodal line and
are branch-scars, while the smaller ones probably represent leaf-
scars.
The roots of S. paradoxa have been found, and closely resemble
those of Calamites (Pennularia). It is doubtful whether the fructi-
fication has ever been discovered.
The ribbed internal casts mentioned above sommeliinnen enense
an innermost cylindrical cast. This is smooth, and probably
represents a cast of a partially hollow pith. Such a structure
has not been noticed before, though I found exactly the same
phenomenon in several examples of the so-called pith-cast of
Equisetites mougeoti, Schimper and Mougeot, from the Bunter of
the Vosges Mountains, which are preserved in the Strasburg
Museum. This plant is there associated in the same beds with
S. paradoxa. Though the smooth outer surface of 1. mougeoti 1s
known, examples with leaves have never been described. The
pith-casts are indistinguishable from those of Schazoneura. Ac-
cordingly it becomes ever clearer that H. mougeoti is merely the
name given to large leafless stems of S. paradoza*. One pvint,
however, is not evident: the smooth external cast seen in #.
mougeott has not, so far, been found at Bromsgrove. Yet the
external surface of the smaller branches is smooth, and we may
probably assume that the larger examples have still to be sought
for.
How far the presence of this innermost cast can be taken as a
distinguishing mark of Schizonewra cannot be determined as yet,
until it has been observed or disproved in other species.
* In this connection it may be noted that Seward (loc. cit. p. 88) figures
as Schizoneura, sp. a, a stem with smooth external surface enclosing a ribbed
pith-cast, similar to both H. mougeoti and S. paradowa, and calls attention to the
resemblance of the whole fossil to the former.
408 Mr Wills, Notes on the genus Schizoneura,
Having now examined what is known of the plant originally
described as Schizoneura, let us turn to a consideration of the
other species, with the special object of seeing whether the genus
is homogenetiec.
Names have been given to seven species ranging in age from
the Permo-Carboniferous to the Rhaetic, while several other
fragments of stems have been referred to the genus. The follow-
ing table gives the distribution in time and space and the chief
characteristics of the various named species.
One or two notes are necessary relative to the table. In
the first place it will be observed that the description of the
nervation of both S. africana and S. gondwanensis differs from
the usually accepted one which states that stout median nerves
are present. I have, however, examined undoubted specimens of
S. gondwanensis at the South Kensington Museum, on some of
which, e.g. No. V. 7099, several distinct fine parallel nerves can
be seen.
The original specimen also of S. africana (Asterophyllites of
Hooker* ) in the Museum of the Geological Society likewise shows
some three distinct nerves down the centre of some of the leaves.
I use the term leaf here, not as Seward has done in redescribing
S. africanat, where he applies the word to what I would call a
sheath-segment, but in the same sense as Schimper and Feist-
mantel.
In the second place, little is known of S. wardi, and the
description given by Zeiller leaves some doubt as to its nature.
It seems, however, possible that the nervation is multiple.
Let us now refer to the table. It is evident at once that
Halle is well justified in classing S. carreret, S. hoerensis and
S.mervant together, and the institution of the genus Neocalamites
appears expedient. The type of plant represented by Schizoneura
(Neocalamites) carreret seems to have been almost world-wide in
distribution in Rhaetic times; so far so, in fact, that the Euro-
pean, Asiatic and African species are almost indistinguishable.
Of the remaining species, S. ward, although but imperfectly
known, appears to have approximated to the Neocalamites type:
yet it may have possessed multiple nervation. In this case, as
it is likely that the nervation is a generic quality, it could not
be easily classed with that group but would fall in more naturally
with the remaining species.
These three, S. paradoxa, S. africana and S. gondwanensis,
agree closely with one another in the possession of a multiple
nervation, in the small number of leaves, and in the usual union
* Bain, A. G., ‘“‘On the Geology of Southern Africa,” Trans. Geol. Soc. Ser. 2,
Vol. vit. 1845-56 (1852), p, 175.
+ Seward, A. C., loc. cit. p. 89.
409
Schimper and Mougeot.
purlesvAn
SOBA YJNOG MeN
vIpuy
BY Oedl
Boy “g
("4 Ystq) pleaessoxy
puysuq pue sovsly
edoing yegue9
Ayyeroues
edoiny ~pue uspedg
BOLITY Ҥ
A[qeqoid pue ulyuoT,
MOTNGIA4STC.
gspeq corey
SoINSBOT
[809 satjonporg seddQ
gelleg BUPApUOy
Jemoy pue seddq
(sorteg
BUBMPUOL) JeMory)
spog IIVQIVY LEY]
(uerut
-19g) solteg y1oynvog
redney
JoMoy pues syjung
,dodnoey jo 41d
JOMOT pUP op yoxue9}0'T
0441p
oTpoRVay
UOZIIOFL
P98]
jo 0130900 UAOpP seAroU
Pyered = oug 4ourjstp
‘gzout Ajqtssod ao ‘eer,
OAOU UBIPSUL JOUTISIP SSO]
IO 910 B 9}N}T}suUOD pus
peuyep.1e9}eq omm00eq UOT
-o UBIPOU OY} UL YOryA
Soul] esojo puv out AIOA
Aq osiMyysue, po}ern4s
ATUAAOJIUN ST Jeo] JO soevzANG
Jeo, ova jo
e14u89 9} UMOp seAtou
TPllered ouy oorty ysvoy, 4V
JIT JO O[pprur
ay} OL pojesorsse
SOAIOU [ol[VIed oul [eIOAeW
uouatoeds
euo UI seAtoU joT[ered
‘gas-asojo AeA ‘ou jo
SOB, ‘PAATOUTUN 9q 07 preg
oF}FIp
poAreuIty
UWOT}ATON
SaaveT oj1s0ddo
aye[nuis Aoyy yuoserd oe
$]UsUIses-Y} Bays OM4 ATMO
UST AA ‘s}UeTIses-qyR0YS
a}8A0 OFUL poyiun ATTensn
‘Ysipeorg “ZZ-O0T tequinyy
qyeeys
oyur peyrun AT[nyyqnop
‘Soave, MOTTBU 2% JnNoQy
S}USUISES-4}BOYS [VIIAES
OJUL poyUQ ~“Aequinu
UL QE JNoge ‘pvoaq ApATET
aor} SOUITY
-eu0S + ‘s}UeTISeS-4} BETS
OJUL.10} 8] pUs SY BOYS OFUL
4siy 48 poytun “peoig ‘MoT
1 pus g ‘SON UI UB} TOMOT
094Tp
saseq ILoqy} 0} dory SABA
-[e Ajqeqord ‘suo, ‘Aus
SOABOT
“UN4STO WT
‘sisuaupapuob °Gg)
TOTTLOZ
‘up.lom *S)
“UI4SIOT
‘puvdUl{D °c
“SNOT
pus ‘duryog
‘nxopp.ind *¢
‘usuoIg
“Upiaut * S|
“doaryag
‘sasuaLaoy *G/
TOTILOT
“1AlALWDI “5
—
(001498 nsues) Joasnoy pus raduiryog ‘vnawoz.yog
NES
[=
————_——————-——r
ITIVH ‘3a720Uy) vI0aN
410 Mr Wills, Notes on the genus Schizoneura, ete.
of the leaves into sheath-segments. Their distribution in time
is also of interest, for this type of Schizoneura appears to have
almost died out before the advent of Neocalamites in the Letten-
kohle and Lower Keuper. It may be that the one type gave
rise to the other, but this does not seem likely. In this con-
nection I would like to point out that Halle comments on
the resemblance and possible relationship of Meocalamites with
Calamites. In the same way, one may draw a comparison between
Schizoneura proper and Grand’-Eury’s Calamodendron type of
Calamite. Thus, the whorls of leaves are separated by long
internodes and the upper branches probably radiated out in all
directions, while the leaves themselves had several nerves instead
of a single median one, all of which facts are points of resemblance
between the two genera. At the same time we must recognise
that, until we know more about the internal structure and fructi-
fication of this important transitional group of the Equisetaceae,
the relations that they bear, both to the Calamites and to the
modern Equiseta, must remain a secret.
Conclusion. The species so far described as Schizoneura may
be divided into two groups. The one has been given the name
Neocalamites by Halle, and includes S. carrerei, S. hoerensis, and
S. meriant. The other may be termed Schizoneura, sensu stricto,
and embraces S. gondwanensis, S. africana and S. paradoxa.
Until we have more satisfactory information about S. wardi we
are unable to decide to which group it belongs.
Mr Lillie, On Petrified Plant Remains, ete. 411
On Petrified Plant Remains from the Upper Coal Measures of
Bristol. By D. G. Lituiez, B.A., Hutchinson Student of St John’s
College. (Communicated by Mr E. A. Newell Arber.)
[Read 7 February 1910.]
In working out the flora of the Bristol Coalfield, which con-
sists entirely of the impressions of fossil plants, I was fortunate
enough to obtain a small quantity of petrified material. This
was entirely unexpected, because no other source of structural
material of Upper Coal Measure Age is known in Britain. Our
whole knowledge of the anatomy of the plants of this period is
entirely founded on Lower Coal Measure material from the York-
shire and Lancashire Coalfields.
The horizon of the petrified material from the Bristol Coal-
field is Upper Coal Measures. This is shown by the associated
impressions, an account of which has recently been published
elsewhere*. The material was obtained from the base of the
Pennant Grit at one locality, Staple Hill, three miles to the
north-east of Bristol.
A sinking for coal which penetrated for about 300 feet, was
made a short time ago in this locality and was abandoned in the
Bristol equivalents of the New Rock Series of Radstock, a short
distance below the base of the Grit. On this level a massive
conglomerate was passed through, the exact thickness of which
does not appear to be known; but the bed was probably of
no great thickness. Mr Bolton, F.G.S., Curator of the Bristol
Museum, who first examined the sinking, pointed out to me
that plant remains occurred, associated with the pebbles, in this
conglomerate, and suggested that 1 should collect the material
for examination.
At the time when I visited the locality the sinking had been
abandoned for some time and the supply was found to be very
limited. It does not appear likely that further material will be
obtainable. This peculiar conglomerate has not been recognised
elsewhere in the coalfield. I understand that Mr Bolton will
publish a full account of this conglomerate, so I need not enter
into further details upon the subject in this note.
The plant remains, associated with the pebbles in the sand-
stone matrix, consist of fragmentary portions of stems and
petioles, thoroughly isolated from one another and varying greatly
in size and diameter. They are calcified, and the structure is
preserved, the preservation being excellent in some cases.
* Lillie, Geological Magazine, Dec. 5, 1910, Vol. vit. p. 58.
412 Mr Lallie, On Petrified Plant Remains, ete.
A large number of them have been isolated from the matrix
and sections cut from them. The greater number of the specimens
consist of decorticated stems of Cordaites, showing the pith and
the secondary wood. This genus appears to be particularly
abundant in this locality. In addition to Cordaites, at least one
example of a new member, either of the same or an allied genus,
has been obtained. The attribution of most of the plants to the
genus Cordaites is borne out by the fact that examples of the
characteristic pith casts, Sternbergia (Artesia), of this genus also
occur in the conglomerate. In addition, a specimen of a well
preserved Myeloxylon, the petiole of a Medullosa, has also been
obtained. A contribution on the detailed structure of these
fossils is in progress.
Mr Thomas, On the assimilating tissues, etc. 413
On the assimilating tissues of some Coal Measure Plants. By
H. HamsHaw THomas, B.A., Downing College.
[Read 7 February 1910.]
The recent work in Fossil Botany has been concerned almost
entirely with morphological and phylogenetic considerations and
little attention has been given to the physiological significance
of the tissues studied. It is, however, very important from all
points of view to study so far as possible the biology and physi-
ology of the fossilised plants. This can be attempted by an
examination of our material from the standpoint of physiological
anatomy. ‘The process of carbon assimilation is one of the most
important of the plant's vital activities and is closely connected
with leaf structure. Very little research has hitherto been done
on the subject of leaf structure in the Coal Measure period, and
at the suggestion of Mr Arber, the author is endeavouring to
obtain more information on this subject.
The leaves of some members of the Calamocladus section of
the Calamites have been studied in detail. They are small linear
structures, almost cylindrical in cross-section. The simpler types
seldom exceed a length of 3 or 4 millimetres, and were about
‘8—I1 mm. broad. They were borne in whorls on long slender,
probably pendulous, stems. In the longer leaves a considerable
portion of the tissue is composed of thick-walled sclerenchymatous
elements which replace the mesophyll, forming a strand on the
adaxial side and increasing in proportions towards the apex of
the leaf. When this strengthening tissue is absent the leaf tissues
present a concentric arrangement, the central vascular bundle
being surrounded first by the bundle sheath and then by the
pallisade tissue.
The mesophyll of the leaf is entirely composed of isolated
cylindrical cells, running perpendicularly out from the bundle
sheath to the epidermis, and forming a continuous pallisade tissue.
These cells are often completely separated from each other by
very large air spaces, and the tissue was consequently of an
extremely spongy character. Though this system of spaces would
provide an ample path for the circulation of carbon dioxide,
it would also probably bring about rapid transpiration. In the
larger leaves it is noticeable that the air spaces are considerably
reduced. There are indications that, as in the pallisade tissue of
modern leaves, the cells were specially modified to absorb a
maximum of the incident light.
VOL. XV. PT. V. 27
414 Mr Thomas, On the assimilating tissues
The stomata were confined to the adaxial side of the leaf,
which in the living state was probably also the lower side. Here
they occur in considerable numbers, one example showing a
distribution of about 440 per sq. mm. They were about ‘024 mm.
long and ‘018 mm. broad. In shape, the guard cells resembled
very closely those of modern Equisetums, and in one specimen
they show also the transverse striations of thickening material,
which are so characteristic of the recent plants. The guard cells
are usually level with the surface of the epidermis but may be
slightly sunk in it. The latter tissue forms a well-marked feature
in the leaves.
Towards the centre of the leaf the pallisade cells abut directly
on the bundle sheath, and are often somewhat enlarged at the
point of contact. This enlargement is a feature sometimes ob-
served in modern plants, and Haberlandt has figured a similar
arrangement in the connection between the “Zuleitungsystem ”
and the “Ableitungsystem” in Cycas circinalis*. There can be
little doubt that the bundle sheath, termed by Hick+ “melasmatic
tissue,’ functioned as the path of conduction for the products of
assimilation. It is a conspicuous feature in most specimens,
because its cells are characterised by the large mass of opaque
carbonaceous matter which they contain. No distinct tissue
can be recognised which could be called phloem, nor can any
sieve tubes be made out. Some leaves show thin-walled elongated
parenchymatous cells associated with the xylem, while in others
this feature is completely absent. In each leaf, however, the
amount of assimilation could not have been large, for the leaves
are very small; the products could easily be conducted the short
distance to the stem by diffusion through the elongated cells
of the bundle sheath.
The cells of the thin-walled inner zone of the cortex of the
young stems often contain black contents like those of the bundle
sheath, and it may be suggested that these also were connected
with the formation of carbohydrates.
It would appear then that in the Calamites the leaves show
a structure adapted for carbon assimilation, even though they
were very small. They were probably produced in large numbers
and were sufficient to provide for the nutrition of the plant.
The leaves of other Coal Measure plants are now being ex-
amined. Some Lepidodendrons possess foliar members in which
we find a considerable proportion of mesophyll, which may be
either of a spongy type composed of rather stellate cells, or in
* Haberlandt, ‘‘ Verleichende Anatomie des assimilatorischen Gewebesystems
der Pflanzen,” Pringsh. Jahrb. 1882, Taf. vt. fig. 15.
+ Hick, ‘‘On the structure ‘of the leaves of Calamites,” Mem. and Proc. Man-
chester Lit. and Phil. Soc. Vol. 1x. 1895, p. 179,
of some Coal Measure Plants. 415
other cases may bear considerable resemblance to the mesophyll
of the Calamites. Tissue of the latter type has also been de-
scribed by Renault* in L. esnostense, where it has the form of
chains of cells with numerous interspaces and united by short
transverse branches.
In material from Shore, Littleborough, Lancashire, leaves
have been found which are probably identical with a type de-
scribed by Felix + from Westphalia some time ago. There is no
record of their previous discovery in this country, and as yet their
- affinities are uncertain. It seems probable that they belong to
some species of Lepidophloios. They are about 6 mm. across, and
fragments over 3 cms. long occur. In these the mesophyll appears
differentiated into spongy tissue and pallisade cells, and thus more
closely resembles that of the higher plants.
In so far as the present work has progressed there would
appear to have been considerable variety in the assimilating
systems of the different members of the Carboniferous flora, and
these may be closely compared with those found in living plants.
* Renault, Flore fossile d’Autun et d’Epinac, Paris, 1896, p. 179.
+ Felix, J., Westphalischen Carbon Pflanzen, Berlin, 1886, Taf. v. fig. 6.
27—2
416 Mr Beatty, The production of Cathode Particles
The production of Cathode Particles by Homogeneous Réntgen
Radiations. By R. T. Beatry, M.A., B.E., Emmanuel College.
(Communicated by Prof. Sir J. J. Thomson.)
[Read 21 February 1910.]
Several physicists have investigated the cathode particles
produced when Réntgen radiations fall upon various substances.
The recent work of Cooksey* and Innest has shown that the
velocities of these cathode particles are independent of variations
in the intensity of the Réntgen radiations used, and are also
independent of the nature of the substance struck, but that the
velocities increase or decrease with an increase or decrease in the
penetrating power of the exciting Réntgen radiations.
The discovery of homogeneous Réntgen radiations, emitted
by certain metals when exposed to suitable Réntgen radiations,
enables one to use definite beams which differ widely in penetrat-
ing power, and it seemed that by using such beams more definite
information might be gained about the cathode particles emitted
from metals placed in the path of such beams.
When a very thin silver leaf was placed in the path of the
homogeneous radiations described above, cathode particles shot
out from its surface. It was determined to investigate the
coefficients of absorption of these cathode particles in air and in
hydrogen. Hydrogen was chosen on account of its anomalous
behaviour with regard to ionisation phenomena.
The radiations from a Réntgen bulb, proceeding in a direction
normal to the plane of the paper (fig. 1) fell upon the metal
which acted as radiator. Plates of Fe, Ni, Cu, Zn, As, Sn were
used as radiators.
A homogeneous radiation then proceeded from the radiator.
Part of this entered the cylindrical brass chamber A through the
thin parchment window. It then passed through the silver leaf,
and was finally totally absorbed in the thick brass disc DD which
served as electrode. DD was covered with paper to prevent the
emission of cathode particles from its surface.
Another portion of the radiation entered the primary electro-
scope (fig. 1), which served to standardise the amount of homo-
geneous radiation emitted by the radiator.
As the quality of the homogeneous radiation is unaffected by
variations in the bulb, and as the quantity of radiation entering
the chamber A is always the same fraction of that entering P
* Cooksey, Am. Jour. Sci., 1v. 24, 1907, p. 285.
+ Innes, Proc. Roy. Soc., Ser. A, uxxtx., Aug. 2, 1907, pp. 442—462,
by Homogeneous Réntgen Radiations. 417
(for a given radiator), no discordance in the results can arise from
variations in the bulb.
The electrode D was parallel to Z and distant 1 cm. from it.
D was connected to the gold leaf of the secondary electroscope,
and could be earthed by a key. The chamber A was kept at a
potential of 200 volts.
When the bulb was in action the air between D and L was
ionised. Thus a charge was given to D, as soon as the connection
to the earth was broken. ‘The method of experimenting was to
vary the pressure of the air inside A, and to measure the ionisa-
tion between D and JL corresponding to each pressure. The
amount of this ionisation was in each case standardised by means
of the primary electroscope.
TO PumP
TO SECONDARY
ELECTROSCOPE
~ Parchment ~
RADIATOR
Primary ec voscope
Fig. 1.
This ionisation is due to two causes: (1) Ionisation due to
X-radiation alone. This has been shown by Crowther* to vary
directly as the pressure of the air. (2) Ionisation due to cathode
particles emerging from Z. The amount of ionisation due to this
source will remain constant as long as the pressure is great enough
to absorb all the particles. When the pressure falls below a certain
value some of the particles will reach D before being absorbed and
the ionisation will decrease.
Fig. 2 shows how the ionisation due to each of these sources
varies with the pressure, and how the actual curve found is the
sum of these separate effects.
* Crowther, Proc. Roy. Soc., Ser. A, uxxxxu., March 10, 1909, pp. 103—127.
418 Mr Beatty, The production of Cathode Particles
Hence given the actual curve we find the part due to cathode
ionisation by drawing through the origin a line parallel to the
straight portion of the curve, and subtracting its ordinates from
those of the actual curve. This process gives the curve showing
the increase of cathode ionisation up to a certain pressure.
The pressure at which the ordinate of the cathode curve is half
the length of the maximum ordinate gives the pressure at which
half the cathode particles starting from Z reach D.
Knowing the distance between D and L (1 cm.), the tempera-
ture of the room, and this critical pressure, we can now calculate
the thickness of the layer of air at 170 mm. pressure and 15° C.
temperature, which would absorb one-half of the energy of the
cathode particles starting from LZ (Table I, column 1).
TABLE I. Avr.
Cathode energy Total cathode
F : ; _, |emerging—~absorp- | energy produced in
Radiator al 1 Gas. MINI C TD tion of X-radiation|} leaf-absorption
in leaf of X-radiation
Fe 00804 87:2 346 30°2
Cu 701349 51-9 O12 26°0
Zn 0164 42-7 O75 24°5
As 0255 | 27-43 1:120 30°8
Sn ‘176 397 6-470 25°7
If we assume that Ce~” represents the amount of energy
which gets through a thickness # (in ems.) of air at normal
pressure and temperature we can now calculate A, the coefficient
of absorption of the cathode particles by air. For when
g=t, Gwahe °. hase
Qu] 7
The values of A are given in column 2.
Further, since the experimental curves can be split up as
shown in fig. 2, we can determine the ratio of the ionisation
caused by the emerging cathode particles to the ionisation due to
the X-radiation in the layer of air between D and £. For the
sake of uniformity we shall measure this X-ionisation when the air
is at a pressure of 760 mm.
This ratio has really a very simple meaning. Barkla and
Sadler* have shown that if we take any two substances which
do not give a homogeneous radiation under the stimulus of a
* Barkla and Sadler, Phil, Wag., Muy 1909, p. 751.
by Homogeneous Réntgen Radiations. 419
certain series of X-radiations, then the ratio of their coefficients
of absorption for this series of X-radiations remains constant for
each one of this series.
Since silver* and air + exhibit no homogeneous radiation when
stimulated by the range of radiations here employed, we may
assume that their coefficients of absorption have a constant ratio
for each X-radiation.
We shall further assume that the ionisation in air is pro-
portional to the coefficient of absorption of air.
Hence ionisation of air «© absorption by air of radiation
absorption by air oo absorption by silver.
-, ionisation of air «© absorption by silver.
ax Cathode ionisation
Tonisation
Pressure of Cir
Fig. 2.
Hence the ratio (Table I, column 3) is a measure in arbitrary
units of the ratio of the energy of cathode particles emerging
from the silver leaf to the amount of energy absorbed by the leaf
from the X-radiation.
From the numbers in Table I, column 3, we can attempt to
calculate the total energy due to cathode particles produced in
the whole volume of the leaf when the leaf absorbs a fixed quantity
of radiation.
Two assumptions must be made:
(1) That each cathode particle moves initially in the direction
of the incident X-radiation.
(2) That these particles are absorbed according to an ex-
ponential law in the silver leaf itself.
These assumptions have not been definitely proved, but there
* Tbid., loc. cit.
+ Beatty, Phil. Mag., Nov. 1907, pp. 604—614.
420 Mr Beatty, The production of Cathode Particles
is evidence in favour of both of them, and they are the simplest
that can be made.
Now if I be the amount of ionisation in air due to the cathode
particles which emerge from the leaf, and % the coefficient of
absorption of these particles in silver, then a simple integration
shows that J is the amount of ionisation which would be caused
if all the cathode particles set free in unit thickness of the silver
were able to spend their whole energy in ionising air instead of
being absorbed by the leaf.
Since for any set of cathode particles the absorption in air is
proportional to the absorption in any other substance*, we may
use the former value instead of the latter, if we are not compelled
to use absolute values.
Hence if we multiply the numbers in Table I, column 38, by
the corresponding values of \ in column 2, we get numbers giving
the amounts of cathode energy liberated by different kinds of
X -radiations when they are equally absorbed in silver. The results
are given in column 4.
These numbers are seen to be of the same order of magnitude
though the numbers in column 3 vary widely. No closer agree-
ment is to be expected considering the three assumptions which
have been made in getting this result.
Hence we are justified in conciuding that the amount of energy
spent by the incident radiation in producing cathode particles is
proportional to the energy of that radiation which is absorbed by
the leaf.
The experiments were now repeated, using pure hydrogen
instead of air in the chamber A. The results are given in
Table II.
TABLE II. Hydrogen.
Radiator din din Range in H,| Total cathode ionisation in H,
cms. | em.’ | Range in air| Total cathode ionisation in air
Fe 0410 17:05 5:12 1:01
Cu 0733 9-55 5°44 99
Zn 0909 cdl 5:54 “98
Sn 1:37 51 Ce 1-00
The first column gives the thickness in ems. of the layer of
hydrogen at 760 mm. pressure and 15° C. required to cut down
the energy of the cathode particles to half its value.
* Lenard, Wied. Ann., Lvi., 1895, p. 255.
by Homogeneous Réntgen Radvations. 421
Column 2 gives the coefficients of absorption by hydrogen.
Column 3 is obtained by dividing the values of X given in
Table I by the corresponding values in Table II. It will be
seen that the ratio increases as the cathode particles become more
penetrating.
Column 4 gives the ratio of the total ionisation produced by
a given bundle of cathode particles in hydrogen to that produced
by the same bundle in air. The ratio 1s unity within the limits of
experumental error.
In Table III are added some data previously found for cathode
rays. It will be seen that the constants relating to the cathode
TABLE III.
Velocity of corpuscles f :
expressed as due to a d for air vk an pe Authority
‘| potential fall in volts yes BASS ohn Ee
4,000 645 144 4:48 Lenard
20,000 31 — — Seitz
40,000 38 “AT 8:05 Lenard
particles due to the Sn radiation are very close to those found by
Lenard for corpuscles possessing a velocity due to a drop of potential
of 30,000 volts.
Relation between the absorption of the cathode particles by air
and the absorption of the emisting X-radiations by aluminium.
This relation was found to be linear, and is shown in fig. 3.
The abscissae are taken from figures due to Barkla and Sadler*,
with the exception of that relating to Sn, for which radiation
it was found by the author that c= 1:65, the absorber being
aluminium.
Relative tonisation in arr and hydrogen due to homogeneous
X-radiations.
The ionisation in hydrogen due to soft X-radiations is so small
that the straight portion of the typical curve shown in fig. 2 was
almost horizontal. A separate set of experiments was made to
determine this ionisation accurately. The silver leaf was removed
from the chamber A and the plate electrode replaced by an
aluminium wire bent into a ring. The ionisation observed in the
chamber when filled with hydrogen and air respectively was then
determined. The results are given in Table IV.
* loc. cit.
422 Mr Beatty, The production of Cathode Particles, ete.
.
TABLE IV.
eae eae as = |
: Tonisation in hydrogen
Radiator —~ a : g |
Tonisation in air
Fe 175
Cu iT
Zn ioe
As Tas
Sn ae
A of Cathode Particles in diy
to
Sie 3.
Note. In a recent communication to Nature (October 28,
1909) Sadler has determined various relations among the cathode
particles excited by homogeneous Réntgen radiations. His results
do not in all cases agree with the relations here described.
I have much pleasure in thanking Sir J. J. Thomson for his
interest in this investigation.
Mr Bateman, Solution of a system of differential equations, etc. 423
The solution of a system of differential equations occurring
in the theory of radio-active transformations. By H. BATEMAN,
M.A., Trinity College.
[Read 21 February 1910.]
1. It has been shown by Prof. Rutherford * that the amounts
of the primary substance and the different products in a given
quantity of radio-active matter vary according to the system of
differential equations,
a
Bn PHM
ee es) i Lge ds ROeeyeeeas (1),
OF =n,R- Ni |
ie ee |
where P, Q, R, S, T, ... denote the number of atoms of the primary
substance and successive products which are present at time 7.
Prof. Rutherford has worked out the various cases in which
there are only two products in addition to the primary substance,
and it looks at first sight as if the results may be extended to any
number of products without much labour.
Unfortunately the straightforward method is unsymmetrical
and laborious, and as the results of the calculations are needed in
some of the researches which are being carried on in radio-activity
the author has thought it worth while to publish a simple and
symmetrical method of obtaining the required formulae.
2. Let us introduce a set of auxiliary. quantities p (a), q (2),
r(a), .... depending on a variable x and connected with the
quantities P(t), Q(t), R(t), ... by the equations,
p(2)= | PIG) Ci, IG) = | Cnt QENbsees.(2):
0 0
It is easily seen that
I ea di=—P(0) +2 | (Soe UG) Cy aco cee ROE (3),
0
= — P,+ ap,
* Radio-activity, 2nd edition, p. 331.
424 Mr Bateman, Solution of a system of differential equations
where p is written for p(x), and P, for P (0), the initial value
of P (é).
Multiplying equations (1) by ¢~*, and integrating from 0 to
2% with regard to ¢ we obtain the system of equations
“xp ae P. = Aip
xq —Q = Ap — And
ar — R, = Aad as Ag?" ain aie nie wirete inledetetenetetaty (4),
vs — So = \a = AAS
from which the values of p, g, 7 may be obtained at once.
If Q=R, =S,=...=0, Le. if there is only one substance
present initially, we have
ae Po pane MPo es Ay AoPo
Pete’ 7 @+A)GEM) TED) GEO.
and for the nth product
Ag +++ Naa lo
o)— hak Le Se LE (REE CIOCOOTOOOGOO .
vile) (a +24) (@ +A.) ... (4+ An) (5)
Putting this into partial fractions, we have
By C2 Cn
ae) Fe ae Gane
Nn Aa age ee,
where a= * ne
7h OSA OFS) OSs
o NiAso<s Anil. 0. eee (6).
B=
Oy >= Qe) (As rc? Az) eee (OM a rz) j
rteits< etc.
To obtain the corresponding function V(¢) we must solve the
integral equation
HOSS i e- N (t) dt.
0
Now it has been shown by Lerch* that there is only one
continuous function N (¢) which will yield a given function »v (a);
hence if we can find a function which satisfies this condition it
will be the solution of our problem. It is clear, however, that
1 =[ ; ea nt dt:
Z+HX 0 ;
hence the above value of v (a) is obtained by taking
UNI) = Grea’ 4 leeks’ tee Ghent hence (ids
where the constants have the values given by (6).
* Acta Mathematica, 1903, p. 339.
occurring in the theory of radio-active transformations. 425
In the case when Q (0), # (0), ... are not zero, we have
iP. MP, Qo
erree ! Gem) a 4
MAsPo Ao Qs fe Ry sod (3)
~ (@ +a) (@+ Ae) (+ Aa) * (ety) (@ + ds) (@ + Ag)
ete.
and we may obtain the values of P, Q, R by expressing these
quantities in partial fractions as before.
The complete solution for the case of a primary substance P
and three products - R, § is
r
P=Pye™, Q=5 > Petts (ee -+Q,)¢ e-t
fal Ddseliy —Ayt ‘, Xr Nee NeQo |e —Ast
x | OOOO A) ene
Ine ery rN 5Q> se =
' R Aol
eee oe
ae ees i
(A, — Ax) (As — — 1) n= Ay)
Tes eo)
iC —Ay Ft
i: lacs LY) (A3— ro) Qu— Ae) As rr A») (Ag TS S| :
+| PEED Wik 1 era.
Ay — ds) (Az — As) (Ay _ ds) On rs) Or, — =e)
ek pia Le a AP,
ee (oN) ZF) (OMe)
ers A; |e =
+ rae
0S SC en ae ee
The solution may evidently be eee, by superposing the
solutions of the cases in which the initial values of P, Q, R, S are
given by
(1) PO)=P,, Q(0)=0, RO)=0, S(0)=0.
2) P()=0, Q(0)=@, R(0)=0, S()=0.
(Ss) en (O) — OF, OO) 0" aha(O) hy, (0) 0
(4) P(O)=0, Q(0)=0, RO)=0, S(0)=S,.
The method is perfectly general, and the corresponding
formulae for the case of m—1 products may be written down at
once by using (6).
The general formula covers all the four cases (Radio-activity,
pp. 331—337). For instance in Case 2 when initially there is
radio-active equilibrium, we have
M% =, 1%, =A5Q5 = Neeley = AySo-
426 Mr Bateman, Solution of a system of differential equations
The solutions are then
n Ny Ay
(pra e ent EEO pa ae eer ae
i, mes TE Een
Non Ayn
RPA 240 Avi ae 10 ew dat
C= c=, (Ay — Ae) (As — Az)
a Ny AyN as
As (A, en rz) (re ae As)
gS AyAzs No 4 =e
CNOS 2) Oyen)
Ay As No
an
BO One Oucs) a
Ay Ag N
sf e~
A, =— Az) Ar — Ns) (Ag = As)
Ny AoAs No
y=) OAs) =A) ©
The solution for the case of n— 1 products is given by
MNS 26.68%,
where the constants c, are obtained by expressing
ee eee
L (V+) (V+As) ... (4 +An)
in partial fractions.
The method by which the solution of the system of differen-
tial equations has been obtained is really of very wide application
and may be employed to solve problems depending on a partial
differential equation of the form
oV OO NG \
at Ge aa
provided the initial value of V is known.
For if we put
ue if “et V(t) dt,
su (s)— Vi= = [ewe at
it appears that w(s) satisfies the partial differential equation
Oia: 2a) \ .
Gx ay’ Ay) =) U+su+V,=0 ecccevces (9).
Further, if V satisfies some linear boundary condition which
18 independent of ¢ the function w will generally satisfy the same
boundary condition. This function (w) must be obtained from the
occurring in the theory of radio-active transformations. 427
differential equation (10) which is simpler than (9), inasmuch as
it depends upon fewer independent variables.
In many cases the solution of the integral equation
uw (s) = [oe V (6) dt
may be calculated by means of the inversion formula *
Vay | eu Oat,
where c is a contour which starts at — 0 at a point below the
real axis, surrounds all the singularities of the function u(¢) and
returns to — © at a point above the real axis, as in the figure.
The conditions to be satisfied by w() in order that this
inversion formula may be applicable have not yet been expressed
in a concise form.
The formula may be used to obtain the solution of a problem.
in the conduction of heat when we require a solution of
CAE OUE
Me 7 Be
which satisfies the boundary conditions
V=0 when w= 0 and «=a,
V =f (x) when ¢ =0.
The solution found in this way is identical with the one given
in Carslaw’s Fourter’s Series and Integrals, p. 383.
* A particular case of this formula has been given by Pincherle, Bologna
Memoirs, 10 (8), 1887.
428 Mr Burnside, On double-sizes.
On double-sives. By W. Burnsipg£, M.A., F.R.S.
[Received 7 February 1910.]
The configuration of twelve lines, known as a double-six, arises
naturally in connection with the theory of cubic surfaces. Its
connection with the theory of quadric surfaces has not, so far as
I know, been investigated. It is the object of the present note
to establish the existence of a double-six from what I believe to
be a fresh point of view, connecting it with a pair of quadric
surfaces that stand in a special projective relationship to each
other. A word of explanation must be given of the digression in
§3. The theory of quadrato-quadratic equations has been very
completely worked out; but the particular relation here required
could not be quoted in a convenient form. It has therefore been
established directly.
1. Let S, 8’ be two quadrics. On each choose one of the two
sets of generators: and let \ be the parameter that distinguishes
one of the chosen set on S, and yw the corresponding quantity for
S’. A generator of S meets S’ in two points, through each of
which will pass one generator of the chosen set on S’. In other
words, if A, # are parameters of two intersecting generators on
S and 8’, they are connected by an equation which is quadratic
in both X and w. Denote this equation by
fi DE OH (i).
Let py, #) be the roots of this equation when X is Ay; Ay, A, the
roots when pw is fy, A+, A») the roots when mw is fw; and so on.
Then there arises an, in general, unending series of quantities
wo Ap fig Lia peLaING Reg Naifer Naens, Sijsc eee aaa (11),
all of which are rationally determinable in terms of any two
consecutive ones. Corresponding to this series there is an, in
general, open polygon whose sides belong alternately to the
chosen generators on S and the chosen generators on S’; and
no side of the polygon meets any other except the two which
immediately precede and follow it. The theory of an equation,
quadratic in both variables, such as (i) is well known. Starting
from an arbitrary pair of values that satisfy it, the series of
values (ii) is in general unending, but if it is periodic for some
chosen initial value of X (or p), 1.e. if it 1s of the form
«2 AnMnAoMoAr fa -- PO ee
then it is periodic for every initial value. Suppose now that
the quadrics S, S’ are such that the polygon is a (gauche)
Mr Burnside, On double-sizes. 429
hexagon. Then the existence of a double-six implies that when,
with the remaining set of generators on S and the remaining set
on S’ the same construction is carried out, the polygon is again
in this case a hexagon. Conversely, a proof that this latter
polygon is a hexagon establishes the existence of a double-six.
2. Any two arbitrary quadrics can, by a suitable projection
(which may be imaginary), be brought to the forms
oe — y? — a2? + DY? =0,
ee — Py —2+?=0.
A generator of a chosen system from each is given by
e+y+nr(az+ bt) =0;
rA(a@—y)+az—bt=0;
and cx + dy+p(z+t)=0;
p(ce —dy)+z2—t=0.
The condition that these should meet is easily found to be
Mw? + A (A? + yw?) + Bd +1=0,
_(at+b)(c+d) pe ny abed + 1
= (a—6)(c—d)’ (a—b)(e—d)’
The equations to the two other sets of generators, and the
corresponding conditions for them are obtained by writing —b
and —d for b andd. It is to be noticed that writing —2 for »
merely changes the sign of B.
— f2 ~
t ZG ) toattye=ris
when. A
1
3. The tangent at (x eon? Saee
x(l—#)+y2t=r(1+F).
If this meets (w+ a)? + y? = F? in the point
1-7? 2
(“+ Ripe Frye),
then {(R—a)—(R+a)t}(1—-#)4+4Rt’ =r(14+f)(1 +#?).
Put VSTIS, 1 Slane: i
then mn?(R—r+a)s’s?—m?(R+r—a)9%—v(R+r+a)s?
+4Rmnss’' + R-r—a=0.
ae mr (R-r+a)=R-r—a,
and m(R+r—a)=n7(R+r+a),
the equation is ;
s’s? + A (s?+ 8”) + Bss’ +1=0,
Gtr 16k
“(Roroe P= Baye
VOL. XV. PT. V. 28
where A
430 Mr Burnside, On double-sixes.
The equation connecting A, w is the same as that connecting
s,s’. Hence if the polygon whose sides lie on the two quadrics
is a hexagon, the circles must be such that the sides of a triangle
inscribed in the second circle touch the first. The conditions for
this are either
(i) @ = R?—2Rr, or (1) a = BR? + 2Rr.
In the first case,
peer Es ee en
r 7
giving . A?—1=+B.
In the second ease,
r 16R?
Fo sagen y Fa
giving A?—1=4+ AB.
(a+ b)(¢+d) abcd + 1
4, If
(a—b)(c—d)’ (a—b)(c—d)
satisfy one of these relations, then obviously
(a — b)(c — a) abcd + 1
(a+ b)(c+d)’ (a+b)(c+d)
satisfy the other. In other words, if for a chosen pair of sets of
generators of the quadrics the polygon is a hexagon, then it is
also a hexagon for the other two sets. As pointed out above,
this is equivalent to establishing the existence of a double-six.
5. If the two quadrics are taken in the usual canonical form
ax? + by? +c2 +d? =0,
av+by+c2+d?=0,
it will be found that the above condition
A?-1=4+B,
which ensures that a double-six lies on them, may be expressed
irrationally in the form
1 1 1
+ = 0.
Vabe'd’ +Va'b’ed = “Vacb'd’ + Va'c'bd is Vadb'c + Va'd'be
Mr Edwards, On the Procession and Pupation, etc. 431
On the Procession and Pupation of the Larva of Cnethocampa
pinvora. By T. G. Epwarps, B.A., Emmanuel College. (Com-
municated by Mr H. H. Brindley.)
[Read 21 February 191 0. |
The following note is a summary of certain observations made
during a fortnight spent at Arcachon, between the 18th and 31st
of March, 1909, a visit which I undertook at the suggestion of
Mr Brindley with a view to clearing up certain points with regard
to the processional larva of Cnethocampa pinivora.
The habits of this peculiar larva were first studied by Réaumur
in 1736, who treated the subject in considerable detail; but as his
material was all conveyed by coach from Bordeaux to his house at
Paris, the conditions under which his experiments were performed
were necessarily somewhat artificial. Ratzeburg also described
the life history, while in the last fifteen years Fabre has recorded
his observations on all stages of this moth, confirmimg many of
Réaumur’s results and adding much to his account of this insect.
Lastly, a paper by Mr Brindley appeared in the Proceedings of
this Society for 1906. In this was given a detailed account of the
behaviour of a certain procession which came under the writer’s
observation, together with certain other points which supple-
mented Fabre’s description.
On warm days in March and April the processions of Cnetho-
campa pinivora are frequently to be observed in the neighbourhood
of the Pine Woods of the Landes, where their nests form prominent
objects among the branches.
The procession is one of single file, the larvae being arranged
in head to tail contact. The whole moves along a silken thread
which is commenced by the leader and added to by all the larvae
in succession. -
The number comprising a procession varies greatly, and though
I saw many processions, I only encountered three which exceeded
one hundred in number. The largest of these was crushed upon
the pavement of a road near the woods, but it measured 26 ft. and
must have contained at least 260 larvae.
Nature of the Procession.
(a) Primite. Several experiments were made with a view to
determining how far the primite may be regarded as the true
leader. It was found—as Fabre states—that any larva could
function as primite, and that all individuals in the procession
28—2
432 Mr Edwards, On the Procession and Pupation
were alike in this respect. Yet—as will be seen later—it was
found that a particular larva, when once entrusted with this
position, usually retained it. On one occasion, however, I saw
a voluntary change of leader, the primite detaching himself and
becoming inserted at the fifth place. It seemed probable, too,
that the primite was capable of taking a real initiative in certain
cases, the remainder following him whether influenced by the same
stimuli or not. This was shown to be the case in
(1) The selection of a path.
(2) Burrowing for pupation.
(3) Forming of a “circulating mass.” (This term is explained
later.)
In the first case at least two external conditions seem to
influence his choice, viz. ight and surface. This was suggested
in the case of a small procession of seven which came under my
observation. I threw the whole procession into the shade and
determined the path taken by the primite by causing a reflected
ray of light to be cast beneath his head. The procession followed
the reflected ray, although only the primite could have been
influenced by this stimulus. In the case of processions which
burrowed for pupation the primite was frequently observed to
test the ground with his mandibles before a circulating mass—
the formation always adopted before burying—was formed.
The term “circulating mass” is used in Mr Brindley’s paper
to denote the assemblage of larvae moving among each other;
but the assemblage, as a whole, remaining on the same spot.
In the formation of the circulating mass, the primite seemed
to be taking the initiative by turning his body sharply round
into a position parallel to that of the second: and if a procession
was reformed without pupation the same larva usually took the
lead. Thus it appears that though any larva can take up the
duties of the primite, yet the primite does in a real sense lead the
procession, the satellites following whether influenced by identical
stimuli or not. At nightfall—according to Fabre—the procession
usually returns to the nest, the primite wandering round until
he strikes the outward-bound thread. I never observed this
proceeding, but if Fabre be correct it would seem that the primite
is capable of exercising choice in this respect. In all the cases
I examined the leader refused to walk along any foreign thread—-
whether artificial (e.g. silk thread frayed out) or that of another
procession—which I placed in his path.
In addition to light and surface, the desire to pupate and
temperature might be suggested as factors influencing the primite
in his movements: and—as Fabre suggests—the occurrence of
processions at all is dependent upon atmospheric conditions; for
in bad weather the larvae remain in their nests.
of the Larva of Cnethocampa pinivora. 433
(6b) The function of the Thread in the Procession. In the
case of a small procession, with the aid of a lens it was easy to
see that each larva secreted its own thread, which was passed
between the pro-legs of the terminal segment. When the path
of the procession became irregular the multiple nature of the
thread was occasionally observed.
In the case of a large procession of 158 the thread became
very thick, in some places a band of silk some 2 or 3 mm. in
thickness being formed. In this case again the multiple nature
of the thread was clearly discernible. In spite of this it does not
seem that it is the thread which guides a satellite in procession
so much as the tail of the larva in front. The following observa-
tion supports this view.
Two sections of a procession—each consisting of seven larvae—
were progressing in the same direction, separated by about
18 inches: the second eventually caught up the first and joined
it, though it did not at any time follow the silk thread laid down
by the latter. On the contrary that thread was crossed several
times, and joining up only occurred when the primite of the
second in his wanderings accidentally struck the sixth larva of the
first procession ; when he stopped immediately until the last larva
had passed and joined on in the right place.
The evidence of artificial breaks is of interest in this connec-
tion. It appeared in all cases examined that touch rather than
sight was the chief guide to the satellites. When larvae were
removed from the middle of a procession, together with the
thread beneath them, joining-up always occurred if the leader
of the hinder portion actually came into contact with any part
of a larva in front. If the thread were left, joining-up was more
frequent, but if the break were small it occurred whether the
thread were removed or not.
These observations tend to show that normally the chief factor
in keeping a procession together is the head-to-tail contact of the
larvae. The thread is of relatively small importance in this
connection, and serves rather as a guide to the primite on his
return journey to the nest. But the fact that joining-up occurs
more readily in the case of small breaks, when the thread is not
removed, would seem to indicate that the touch of the thread
may under certain conditions act as a guiding influence to the
satellites,
Method of Formation of the “Circulating Mass.”
When on the march, processions were frequently observed to
form “circulating masses.” This formation is usually adopted
43.4 Mr Edwards, On the Procession and Pupation
immediately before burrowing for pupation: but at other times
it may result from a variety of causes, amongst which may be
mentioned fatigue and external interference, and sometimes for
no apparent reason at all. Fabre suggests cold and darkness as
influences.
When I caused a small procession to circulate in a closed
orbit, a circulating mass was formed after 24 revolutions by the
gradual diminishing of the diameter of the circle, a process which
tended to crowd out some of the larvae. From this mass a pro-
cession was subsequently reformed. When formed from a straight
procession the method of procedure is somewhat complicated.
The primite appears to start the formation by assuming a zig-zag
mode of progression, which is followed for a time by the satellites.
The arrangement soon becomes obscure and difticult to follow,
but there are certain noteworthy features in the behaviour of the
satellites.
On entering the mass the larvae do not come to rest, but
continue to move slowly and in a very characteristic way, all the
time moving their heads rapidly from side to side and depositing
their threads. If the procession be a large one, the satellites
entering into the newly-forming mass soon begin to crowd one
another out in their efforts to reach it, until ranks of four or five
deep are formed. The thread in these places takes a similar
course. During the day the circulating mass formation may be
maintained for an hour or two; but if at the end of that period
the larvae have not begun to burrow, it is usually abandoned in
favour of the procession.
The manner in which the procession is reformed is of consider-
able interest. By marking alternate larvae (by means of fine sand
or flour scattered over the dorsal papillae) I found that the
original order of the procession was not retained; but in every
case I observed (five different processions*) the primate of the
resulting procession was the same as that which went into the
circulating mass.
Shortly before the primite sets out a rough kind of arrange-
ment is sometimes to be observed in the mass, many of the larvae
being arranged with their heads directed towards the point at
which the procession is to start. The whole process of reformation
is a very orderly one, though the order in which the larvae “fall in”
is not in every case obvious.
In the case of a large procession which I photographed in the
act of reforming the single-file formation, there was an arrange-
ment of larvae four or five abreast in the neighbourhood of the
mass, similar to that observed during its formation.
* The largest a procession numbering 57 larvae.
of the Larva of Cnethocampa pinivora. 435
Purpose of the Circulating Mass.
It is possible that the circulating mass is sometimes formed
for the purpose of pupation, but again abandoned for the normal
procession on account of the unfavourable nature of the ground
in the spot selected. But this explanation cannot apply to the
majority of cases, for processions are of normal occurrence through-
out the insect’s larval existence.
Whether or not the circulating mass be a “rest formation”
(as has been suggested) it is not impossible that it may possess
other advantages as well. The facts already mentioned suggest
the possibility of there being a regular arrangement within the
circulating mass itself. In this case the formation might be a
means of altering the order of the larvae whilst retaining the
same leader. Other facts may be mentioned pointing to the
same conclusion. Processions arranged artificially, by removing
larvae at random from a mass and placing them in a position
of head-to-tail contact, were not found to retain their original
order for very long. A circulating mass was always formed and
a different order arranged for the subsequent procession. The
formation of a mass, in this case, however, was due probably to
external interference rather than to any fixed habit of altering the
order of the procession.
Method of Pupation.
Larvae which had become isolated, from any cause, were
observed to bury themselves in the soft sand by means of their
mandibles; but as a general rule processions seemed to burrow
collectively in the following way. A circulating mass was first
formed in a position which the primite apparently selected, after
testing the consistency of the sand with his mandibles. On two
occasions, which came under my observation, the process differed
slightly, in that the original procession voluntarily broke up into
several smaller processions of twenty or so each—in a manner
similar to that described by Fabre—each of which formed a
circulating mass and buried itself independently. As soon as the
circulating mass was formed the whole commenced to rotate, thus
producing a depression in the sand which gradually deepened.
The sand was at the same time loosened, and some was thrown up
on to the top of the mass. All the while the larvae were deposit-
ing their silk threads until a regular network was formed round
the mass, in which sand became entangled. In some cases the
lower larvae appeared to assist in the process by attacking the
sand beneath with their mandibles. As the process continued
436 Mr Edwards, On the Procession and Pupation, ete.
the whole mass gradually became engulfed, and finally, in the
course of a few days, reached a depth of several inches.
When large processions became buried in this way, without
first fragmenting, bundles of considerable size were formed.
I discovered one numbering more than 100, buried at a depth
of 3 inches. Some of these I removed with the sand containing
them. These completed pupation 19 days after burrowing.
Conclusions.
The facts recorded in the previous observations all seem to
support the conclusion that, though the individuals of a procession
may act alike when influenced by the same stimuli, yet each larva
is capable of independent action. (Cf. voluntary change of leader,
action of primite under special conditions, fragmentation of pro-
cessions occasionally preceding pupation, etc.)
If this be so the procession cannot be said to act in any real
sense as a single individual.
Fabre states that the poisonous properties of the larval epi-
dermis are exceedingly severe in some cases; yet, if this be true,
the effect must depend largely upon the individual. I was not
affected at all, though I was handling the larvae for several hours
at atime. Mr Brindley also found no irritation from the larvae,
though the Tachinid flies which he observed laying their eggs in
a procession were noticed by him evidently to fear and avoid the
hairs. I was told, however, by an inhabitant of the district, that
some persons were subject to a rash at the time when the pro-
cessions were abroad. This is said to be produced by the fine red
hairs of the dorsal papillae which float in the air.
LITERATURE.
Réaumur, 1736, Mémoires pour Vhistoire des Insectes, 1. pp. 149—161.
Fabre, circa 1898, Souvenirs Entomologiques, sér. v1. pp. 298—392.
Ratzeburg, 1840, Forst-Jnsecten, 11. p. 128, and Stettiner Hntomologische
Zeitung, p. 40.
Brindley, 1906, Proceedings of Camb. Phil. Soc. Vol. xtv. Part 1.
Mr Glasson, Secondary Réntgen Rays from Metallic Salts. 437
Secondary Réntgen Rays from Metallic Salts. By J. L.
GLAsson, 1851 Exhibition Scholar of Adelaide University, Gon-
ville and Caius College. (Communicated by Prof. Sir J. J.
Thomson.)
[Head 14 March 1910.]
L
It has been shown by Barkla that when an element of atomic
weight greater than that of Calcium is struck by a primary
X-ray beam of suitable hardness, then the secondary X-rays
emitted by it form a homogeneous beam characteristic of the
radiating element.
The object of the present experiments was to determine
whether the nature of this characteristic secondary X-radiation
is affected by the state of chemical combination of the element.
Barkla made some experiments to test this point (Phil. Mag.
June 1906), but that was before the conception of “ character-
istic homogeneous radiation” was introduced. The enormous
simplification brought about by its introduction, makes further
experiments interesting and their interpretation simple.
In particular it was desired to investigate the effect of a
change in the valency of the metal upon the characteristic
radiation from it.
Il.
The arrangement of the apparatus is shown in figure 1. The
metal or salt to be exarnined was placed at A, the salt being
contained in a thin paper tray about 1 cm. deep. B and C are
two thick lead screens, 20 cm. apart with apertures 2.cm. square
cut in them. The rays enter the ionisation chamber D by a
window of aluminium leaf W, and the ionisation produced is
measured by a Wilson electroscope and a stop watch. No balance
chamber was used as it was found that the coil, fitted with a
hammer break, gave a very constant discharge; the variations
in a series of consecutive readings amounted to about two or
three per cent.
The screens for absorbing the rays were placed at B. They
were of aluminium when an absolute determination of the ab-
sorption coefficient was required; but in some cases filter papers
were used when only comparative measurements were required.
The absorption curve was determined in the same way as that
used by Barkla in his work on homogeneous X-rays. The per-
centage absorption caused by a given screen (II) was measured,
after different proportions of the beam had been previously
438 Mr Glasson, Secondary Réntgen Rays from Metallic Salts.
absorbed by the screen (I). If a curve is plotted, having as
ordinates the percentage drop caused by the fixed screen (II), and
as abscissae the amount previously absorbed by screen (I), then
if the beam is absorbed exponentially, the curve obtained will be
a straight line parallel to the « axis.
>to cells.
200 volts.
Fig. 1.
IIT.
Some of the curves obtained in this manner are shown in figs.
2, 3, 4, and 5.
The curves obtained when the radiator A is a pure metal
are straight lines. These are inserted for comparison. The
curves obtained with metallic salts are all of the same general
nature. They are initially horizontal and then tend downwards.
The point at which the curves begin to show this downward
tendency depends on the salt used and on the hardness of the
bulb.
Mr Glasson, Secondary Réntgen Rays from Metallic Salts. 439
3 Filter papers.
Screen (II)
Fig. 2.
440 Mr Glasson, Secondary Réntgen Rays from Metallic Salts.
The value of the absorption coefficient calculated from the
initial straight portion is always the same as that obtained for
the characteristic radiation from the pure metal. The radiation
from the salt thus consists of two parts:
(i) the homogeneous radiation from the metal,
and (ii) mixed with this is a “scattered” radiation due to the
acid radicle considerably harder than (i).
The proportion of this scattered radiation varies with the hard-
ness of the bulb. It is generally very small and hence does not
evidence itself until the radiation has been very much reduced
by screening. This has the effect of cutting off the soft “ homo-
geneous” radiation much more than the hard “scattered,” and
hence the latter is shown to better advantage. The smallness of
the amount of scattered radiation due to the light atoms is well
shown in the case of Ammonium ferrocyanide. In this salt the
weight of iron in the molecule is only about one-sixth of the
whole. Yet the radiation due to the light atoms does not evi-
dence itself until a considerable portion of the beam has been
absorbed.
The information supplied by these curves may be summarized
thus:
(1) The value of the absorption coefficient for the metallic
radiation is unaffected by its combination with an acid
radicle.
(2) It is independent of the valency of the element in the
compound. This is well shown by the series of iron
compounds FeSO,, Fe,O,, and Fe,O;.
(3) The element may even occur in the acid radicle itself
without affecting the value of 2.
IV.
In this way it is possible to determine 2 for some metals which
it is impossible or inconvenient to use in the uncombined state.
This has been done in the case of Manganese. The salt used
was the sulphate; the curve is shown in fig. 5. The value of X
obtained from the initial part of the curve is 100. This value
agrees with that predicted from its atomic weight, using Barkla’s
curve (Proc. Camb. Phil. Soc. Xv. 257).
I desire to thank Sir J. J. Thomson for his interest in these
experiments.
Mr Glasson, Secondary Rontgen Rays from Metallic Salts. 441
0 10 20 30 40 50 60 70 60 90
Fig. 3. Screen (I1)=Aluminium (pd=:017).
Fig. 4. Screen (II1)=5 Filter papers.
Fig. 5. Screen (II)=Aluminium (pd=-008).
442 Mr Crowther, On the Transmission of B-rays.
On the Transmission of B-rays. By J. A. CRowTHER, M.A.,
St John’s College.
[Read 14 March 1910.]
§ 1. The problems connected with the transmission of 8-rays
through matter are of considerable theoretical importance. Un-
fortunately they are involved at present in considerable obscurity,
and a fairly extensive study by various experimenters has so far
only served to demonstrate the complexity of the phenomena.
The present paper deals only with a few of the many questions
involved.
§ 2. The first question to be considered is the nature of the
absorption itself. The absorption of the B-rays is almost invariably
measured by finding the diminution in the ionization produced
by them in some suitable ionization chamber, when various
absorbing media are interposed in their path. This absorption
may be due to two causes :—
(1) toa loss of velocity by the 8-particles, such as is found
to take place during the absorption of the a-rays ;
(2) to an actual decrease in the number of the @-particles
themselves, due either to stoppage or deflection.
To decide this question it is necessary in the first place to
determine the velocity of a homogeneous beam of §-particles
before and after transmission through a suitable thickness of
absorbing material. 5
A certain amount of indirect evidence already exists on the
subject. In 1907 H. W. Schmidt* performed an experiment
which at the time seemed to prove conclusively that the @-rays
suffered no change of velocity even when transmitted through
very considerable thicknesses of absorbing material. The essential
features of his method are simple, and may be described here as
they form the basis of the methods employed in the present
experiments.
Three circular holes (fig. 1) are made in three lead screens, so
as to define an arc of a circle of suitable radius. The system is
placed between the poles of an electromagnet so that the magnetic
field is perpendicular to the plane of the circle. By a suitable
adjustment of the strength of the field a beam of @-rays entering
the magnetic field at A can be made to describe the circular path
ACB, and will produce ionization in a chamber placed at B.
The velocity of the rays transmitted through this system is known
from the value of the magnetic field, and the radius of curvature
of the path,
* Phys. Zeit. Vol. vit. p. 371.
Mr Crowther, On the Transmission of 8-rays. 443
Schmidt placed at. A a screen covered with radium £;
measured the ionization produced above B, for different values
of the magnetic field, and so obtained a curve connecting the
intensity of the radiation passing through B with the magnetic
field. The curve he obtained shows a fairly sharp maximum
ionization for a certain definite field from which it falls away
gradually to zero, as the field is increased or diminished.
Various thicknesses of aluminium were then interposed between
the radium # and the aperture A and the experiment repeated.
In every case the curves, though decreasing in height as the
absorption increased, were exactly similar in shape and there was
no perceptible shift of the maximum in either direction. From
this result it was argued that no change in the velocity of the
rays occurred during their passage through the aluminium.
Fig. 1.
There is, however, a certain ambiguity connected with the
use of the magnetic deflection method, which under the best
of circumstances can only be minimised, and never completely
eradicated.
If the apertures have a finite size, as must always be the case
in practice, the path ACB is not the only possible path for rays to
follow in order to emerge through B. A little consideration will
show that rays of uniform velocity, but entering the field obliquely,
444 Mr Crowther, On the Transmission of B-rays.
may be transmitted through the system along paths such as acb
or a’c’b’, even when the field is too strong or too weak to deflect
the rays, incident normally, along the path ACB. In this way
even if the rays are of uniform velocity to begin with, there will
be a definite range of field strength throughout which the rays
can pass through the system. Similarly, if the rays are not
homogeneous to begin with, if we are dealing with the whole of
the ®-rays from radium for example, there will be for every
magnetic field a finite range of velocities which the ®-rays may
possess and still be able to pass through the system; and if the
size of the apertures is considerable compared to the radius of
the path, and if the incident beam is of a fairly wide angle, this
difference of velocities may be very considerable. We shall return
to this point later.
In addition to the broadening of the curve due to the finite
width of his apertures, there was a second possible explanation of
the shape of Schmidt’s curves, namely that the rays from the
radium H were not homogeneous.
It was natural to assume that the @-rays from a single homo-
geneous substance were homogeneous. In this case the fact that
the maxima of the different curves always occurred for the same
magnetic field, however much aluminium had been traversed,
would prove that the rays kept their velocity unaltered during
their passage through the fire.
In a recent paper W. Wilson* has given considerable indirect
evidence to show that the @-rays from a single radio-active
substance are not homogeneous, and in this case Schmidt’s curves
could only be explained on the assumption that there was a definite
decrease in velocity as the rays passed through increasing thick-
nesses of absorbing material. In brief, if the finite width of
Schmidt’s curves are due to the rays from the radium # having
a definite range of velocities, as the faster rays are proportionately
less absorbed than the slower rays, for any given thickness of
aluminium, the maximum should gradually move out in the
direction of the stronger magnetic fields, and the higher velocities,
in the absence of any compensating change of velocity in the rays.
From these considerations Wilson is able to deduce the change
in velocity of B-rays for different thicknesses of aluminium. He
calculates thus that the velocity of certain of his rays changed
from 2°78 x 10” ems. per sec. to 2°69 x 10” cms. per sec. in passing
through 0°489 mm. of aluminium.
It must not be forgotten, however, that the experiments of
Schmidt, whichever way we regard them, do conclusively prove
one important fact, namely that the Q-rays from a single radio-
> StlV€ SUUsvace are absorbed in such a way that the distribution
* Pr Roy. Soc. A, Vol. uxxxu. 1909, p. 612.
Mr Crowther, On the Transmission of B-rays. 445
of velocities in the beam remains the same whatever the thickness
of absorbing material traversed.
Under these circumstances it was felt that some more direct
experimental evidence on the point was desirable.
The method employed consisted, briefly, in forming a beam of
homogeneous f-rays by means of the magnetic deflection method
described above, and measuring the velocity of the rays so obtained
by means of a second similar system of screens. Sheets of different
absorbing materials could be placed in the path of the rays be-
tween the two systems, and the velocity of the rays before and
after passing through the absorbing medium could be directly
determined.
As has been already explained, the magnetic deflection method
only gives a truly homogeneous beam of rays when the apertures
are infinitely small. On the other hand only a limited quantity
of B-rays at the best can be radiated by any radio-active substance
through a given area. The dimensions of the apparatus used,
therefore, represent a compromise between these opposing factors.
A further point has also to be considered, namely the possible
scattering of the rays during their passage through the air.
Recent experiments* show that if the path is at all long, the
scattering of the rays by the air may be very considerable. It is
possible that this effect may not seriously affect the purity of
the rays transmitted, but in cases where it is desired to work
with a nearly parallel pencil of rays (as in experiments to be
described later) it is certainly of very considerable importance. It
was decided, therefore, that the whole operation of deflecting the
rays and forming them into a pencil should take place in vacuo.
The form of apparatus finally decided upon is shown in section
in fig. 2. The portion HFGH is placed between the poles of an
electromagnet, so that the edges of the pole pieces lie along LF,
and FG. The tube DA projects from the magnetic field and is
carefully screened by a thick block of soft iron, so as to cut off as
far as possible any strong field from this part of the path.
Windows of thin aluminium foil (‘002 cm.) close the apertures at
A and B.
The radius of curvature of the path of the rays is 4 cms. and
each of the apertures A, D, C, B is 0°5 cm. in diameter. The
distance AD is 3°5 cms. and the depth of the box at right angles
to the plane of the paper is 15 cms. The different apertures are
bevelled, and the screens and sides of the box coated with
aluminium foil to avoid as far as possible any secondary radiation.
The apparatus could be exhausted by means of a water pump to
a pressure of about 12 mm. of mercury, which was found to be
* J. A. Crowther, Proc, Camb. Phil. Soc, Vol, xv. 1909, p. 273.
VOL. XV. PT. V. 29
44.6 Mr Crowther, On the Transmission of B-rays.
sufficiently low for all practical purposes. In experiments for
which a parallel emergent beam was not necessary, the radium
was placed at A. If, however, a parallel beam was desired (as in
the experiments on the absorption of the rays to be described
later) the apparatus was reversed and the radium placed at B.
Two such chambers were made, and placed so that the window
A of the one came directly opposite the window B of the other.
The two magnetic fields were arranged so that rays of the proper
velocity would be deflected round the two systems and emerge
finally into an ionization chamber of the usual pattern.
A
~~ od
= Ba 7) | SE
pee U3]
ZZ
FE’
H
Fig. 2.
The measurements of the ionization produced were made by
means of the compensating method devised for experiments on the
scattermg of the 8-rays from uranium, and fully described in
a previous paper*. In brief it consists in compensating the
ionization current through the first chamber by an opposing
ionization current from a second chamber connected to the
same electroscope, in which the ionization can be varied, in a
* J. A. Crowther, Proc. Roy. Soc. A, Vol. uxxx. p. 186.
Mr Crowther, On the Transmission of B-rays. 4AT
known manner, by means of a shutter sliding over a plate of
uranium oxide. By placing a second small sample of radium
near the compensator, the y-ray leaks through the two chambers
could be made to exactly neutralize each other, and thus the
effect due to the @-rays alone could be measured directly.
Unfortunately the double system transmitted so very few
B-rays that it was not found possible to measure the effect on the
velocity of interposing different screens between them. Enough,
however, was transmitted to test the efficacy of the systems as a
means of producing a beam of homogeneous rays. Keeping the
first field constant and varying the second it was found that when
the mean velocity of the rays transmitted through the first system
was 2°77 x 10” cms. per sec., the extreme values for the velocities
[
of the rays, as measured by means of the second system, were
2:75 x 10 cms. per sec. and 2°79 x 10" cms. per sec. The extreme
velocities of the rays transmitted through one of the systems
therefore do not differ by more than one per cent., plus or minus,
from the mean value, and the system may be regarded therefore
as giving a fairly homogeneous pencil of rays.
In order to be able to work with absorbing screens it was
necessary to make a further compromise in order to obtain a
measurable effect. The first system was left unaltered so that
a homogeneous pencil of rays of known velocity fell upon the
screen. The distance AD in the second chamber was, however,
reduced tol cm. The field across the first system in any given
experiment was kept constant while that across the second was
29—2
448 Mr Crowther, On the Transmission of B-rays.
varied. In this way curves connecting the intensity of the
§-radiation passing through the second system with the magnetic
field both with and without an absorbing substance between the
two systems could be obtained. The experiments were then
repeated for different values of the first deflecting field, that 1s, for
different velocities of the incident rays.
Specimen curves, obtained with aluminium as the absorbing
substance, are given in fig. 3. It will be seen that there is a con-
siderable broadening of the curves even when there is no absorbing
screen in the path of the rays. As the rays emerging from the
first system have been shown to be very nearly homogeneous, this
broadening is due to the greater latitude of path allowed by the
second system owing to the shortening of the tube AD. It will
be noticed that for aluminium this broadening of the curves is
no greater with than without the absorbing layers.
Fig. 3 shows the effect of interposing a sheet of aluminium
0-47 mm. in thickness between the two systems, for two different
velocities of the incident beam. The upper curve in each case is
the curve obtained for the incident beam in the absence of the
absorbing sheet. The ordinates represent the intensity of the rays
passing through the two systems, as measured by the ionization
produced ; the abscissae measure the magnetic field acting upon
the second system.
It will be seen that in each case the introduction of the
absorbing sheet produces a very definite displacement of the curve
in the direction of the smaller velocities.
The actual figures deduced from these curves are given in
Table I.
TABLE I.
Aluminium (0:47 mm.).
Percentage absorption of
Velocity of incident rays | Velocity of emergent rays rays by the Aluminium
2-735 x 10 cm./sec. | 2°690 x 10" cm./sec. (a
2°903 x 10” cm./sec. | 2°881 x 10! em./sec. 52 °/,
It is evident therefore that there is a small, but perceptible
decrease in the velocity of the @-rays as they pass through
absorbing media.
But though this small decrease in velocity accompanies absorp-
tion, it is not sufficient to account for it. The third column in
Mr Crowther, On the Transmission of B-rays. 449
the table gives the percentage of the incident rays absorbed in the
aluminium sheet used; and it will be seen that while 71°/, of the
softer rays are absorbed in the aluminium screen used, the change
of velocity is only of the order of about 2°/,. Allowing for the
change in mass of the @-corpuscles with change in velocity, which
is fairly rapid at these high velocities, this corresponds to a loss
of energy by the @-rays of about 10°/... Only a small portion
of the whole absorption of the rays can therefore be due to
this gradual decrease in velocity. For the main causes of absorp-
tion we must seek elsewhere. However, as we shall see later, the
gradual change in velocity of the rays may have a very appreciable
effect in modifying the shape of the absorption curves.
Glass screens gave very similar results to aluminium. Platinum
on the other hand behaved quite differently. The curves obtained
between the intensity of ionization and the strength of the second
magnetic field were low, showed no decided maxima, and were
very much broadened out in both directions, but particularly im
the direction of the softer rays. On account of the very small
amount of radiation transmitted for any given field it was not
possible to determine the exact shape of the curves at all accu-
rately. Some of the broadening may have been due to the rays
on the whole emerging from the platinum more obliquely than
from aluminium or glass, but 1t seems too great to be altogether
explained on this assumption, and more probable that a homo-
geneous pencil of 8-rays after passing through a platinum screen
emerges with a very considerable range of velocities. This effect
must be connected with some secondary radiation excited in the
platinum. We shall return to this point later.
§ 3. On the absorption of homogeneous B-rays.
The absorption of the 8-rays from a single radio-active sub-
stance, such as uranium X, or one of the radium products, may be
measured by interposing screens of absorbing material of different
thicknesses between the radiating layer and an ionization chamber,
and measuring the change in ionization produced. If the absorb-
ing material is of low atomic weight the absorption curve can be
represented accurately by the equation
f= Tet
where J is the intensity of the radiation after passing through a
thickness d of absorbing material, and 2 is a constant. If the
absorbing substance is of high atomic weight, there is a short
initial steeper portion before the curve assumes the true expo-
nential form.
This law has been tested by many observers for practically all
450 Mr Crowther, On the Transmission of B-rays.
substances emitting 8-rays over a very wide range of absorptions.
N. R. Campbell * found that for aluminium the exponential law
was certainly true to within 0°5 °/, even when the rays had been
reduced to one hundredth part of their initial intensity.
W. Wilsont, on the other hand, using a magnetic deflection
method, found that the absorption of the “homogeneous” rays
obtained by the magnetic deflection method certainly did not
follow an exponential law, but a law which was practically linear.
It is difficult to conceive any mechanism which would produce
a linear law of absorption. Wilson, who worked principally with
aluminium, notes that tin showed some departures from the linear
law, but does not state either the nature or amount of these
departures. It seems probable, therefore, that the linear law found
for aluminium is only approximate and represents the balance of
a variety of causes and conditions.
For example the gradual change of velocity of the @-rays in
their passage through the aluminium would tend to transform an
exponential law of absorption into a law which might approximate
to a straight line. For consider a beam of homogeneous #-rays of
velocity v,and with a coefficient of absorption X. If the exponen-
tial law is accurately obeyed, and if the rays retain their original
velocity, the curve connecting the logarithm of the intensity with
the thickness of material traversed will be a straight line. As
a matter of fact, however, after passing through a thickness d of
material, the velocity of the rays has diminished to v’, and the
coefficient of absorption has increased to some value \’. Since »X
varies rapidly with v (probably as the inverse fourth power of v)
the change in A will be quite perceptible even if the change in
velocity is only small. Thus a change of velocity of only 2°/,
such as was found to occur in 0°47 mm. aluminium might produce
a change in » of as much as 16 °/,. Thus instead of the curve
for log I being a straight line it would be some curve falling
below this line, and its slope, which gives the value of X, becomes
steeper and steeper as the thickness of material is increased.
In fact we should have a curve similar in appearance to that
given by Wilson for the absorption of homogeneous f-rays by
aluminium ft.
Prof. Sir J. J. Thomson§ has very recently published a theory
of the transmission of the 6-rays through matter, according to which
the absorption of homogeneous rays should vary as (1—e-*”), where
a is the thickness of material traversed, and / is a constant. This
would give an absorption curve decreasing at first very slowly,
* N. RB. Campbell, Phil. Mag. Vol. xvi1. 1909, p. 180.
+ W. Wilson, Proc. Roy. Soc. A, Vol. uxxxi1, 1909, p. 612.
+ Wilson, loc. cit. p. 616. Fig. 4.
§ Proc. Camb. Phil. Soc. Vol. xv. Part v. 1910.
ed
Mr Crowther, On the Transmission of B-rays. 451
then much more rapidly, and finally tailing off into something not
very distinguishable from the ordinary exponential law.
The experiments now to be described have been made with a
view to testing the various points briefly touched upon above; and
to ascertain as exactly as possible the true shape of the absorption
curve for some different substances.
The apparatus used is sketched in fig. 4 The radium in a
glass tube is placed at R in the centre of a large block of lead.
A is one of the systems used for obtaining a homogeneous beam
of B-rays, fully described in the previous section of this paper
and sketched in fig. 2. Dis the ionization chamber into which
the @-rays pass. It is made of a copper hemisphere 12 cms. in
diameter, with an inner electrode e of aluminium leaf, and a
large opening dd, closed with thin aluminium leaf to admit the
rays. The absorbing sheets can be introduced into the small
Fig. 4.
space left between the exit tube Band the window d, by means
of a metal slide not shown in the figure. Cis the shutter com-
pensator described in detail in a previous paper, and W an inclined
gold leaf electroscope which differs from the original design in
being only 1 cm. in depth. This variation has the advantage that
it allows of the use of fairly high power objective and thus of a
considerable degree of magnification in the reading microscope.
C and D were charged to opposite potentials and their inner
electrodes were connected through the key K to the electroscope
W by wires passing through earthed metal tubes. These tubes
were filled with sulphur and the key K was made small in order
to reduce as much as possible the leakage from the electrodes
through aiv ionized by y-rays from the radium.
4,52 Mr Crowther, On the Transmission of B-rays.
The chief points in the method are therefore, briefly, as
follows:
(1) The homogeneous rays are produced by magnetic de-
flection through a suitable system of apertures in a vacuum.
(2) They fall upon the absorbing sheet normally, in a
narrow and nearly parallel pencil.
(8) The intensity is measured in an ionization chamber of
such a form that, at whatever angle the rays emerge from the
absorbing sheet, their length of path in the chamber is practically
the same.
TABLE II.
Thickness #, in cms. T/Iy logs) L/L £ logy, (1 — 1/Ip)
Aluminium :
002 1-00 = —
004 996 — (- 010)
012 -95 1-98 — ‘016
033 “7 89 —-021
049 62 ‘79 — :020
073 “29 46 —-010
‘110 12 ‘08 = 07
Platinum :
0) 1:00 = —
00107 al 1:85 — 00058
-00220 ‘D3 (S} (E)
00327 38 58 69
‘00556 AS} 36 61
It may be permissible to note in passing the advantages pos-
sessed by the compensator method in experiments of this kind
over the ordinary methods of timing the leaf over a given number
of divisions. These are, in brief,
(1) The large y-ray leak through the ionization chamber is
balanced by a similar leak through the compensator. In this way
the effect due to the @-rays is measured directly, and not as
a difference between two other large quantities.
(2) The results are not affected by defects in the insu-
lation, as is the case when a timing method is used. As a defect
in the insulation only comes into play when the gold leaf system
begins to charge up, it cannot affect the direction in which the
leaf begins to move, and hence cannot affect the final balance.
In a timing method, however, defective insulation will alter the
Mr Crowther, On the Transmission of B-rays. 453
rate of leak, and may cause considerable errors in the results.
This point is of special importance in the present case, as it is
always difficult to secure really good insulation in the presence of
the y-radiation from any considerable amount of radium.
(3) The method is found to be very convenient in use, and
capable of very considerable sensitiveness and accuracy.
Experiments have been made so far on aluminium and
platinum. The results obtained are given in Table II, and are
represented graphically in figs.5 and 6. The abscissae represent
nae oe
CNS col
ee
ae eae
Seal ea
Ne
1-0 7°
rt
0) 05 10 m
Fig. 5.
in every case the thickness of the absorbing layer; the ordinates
represent in the case of the full curves the corresponding values
of Z/I, and in the case of the dotted curves the values of log, Z/J).
It will be seen that the two substances behave quite differently
in their absorption of the @-rays, and we will consider each
separately.
The curve for aluminium at first descends very gradually and
the quantity of rays absorbed increases very slowly with the thick-
ness during the initial stages. On adding further thicknesses,
however, the curve begins to descend more rapidly, and for part
of its course becomes practically a straight line. For greater
454 Mr Crowther, On the Transmission of B-rays.
thicknesses still the curve has another point of inflection; the
absorption becomes less rapid, and the curve appears to become
asymptotic to the axis of w The small amount of rays trans-
mitted by these thick sheets did not allow of any very exact
determination of the shape of this part of the curve. The ex-
periments seemed to indicate, however, that it did not depart
widely from an exponential form.
It will be seen that the curve thus obtained agrees well in
its main outlines with the form of absorption curve predicted by
Prof. Thomson’s theory. It shows the same initial flat portion,
the steeper middle portion and the final gradual tailing away.
1-00
-80
-60
2 4.0
20
Fig. 6.
More than a general resemblance could not well be expected.
Prof. Thomson’s theory applies rigidly only to thin sheets of ab-
sorbing media. Again the factor / in the equation
I[=I,(1 —e**) i
is a function of the energy of the rays, and decreases as the energy
is diminished. As the energy of the rays is continually diminish-
ing during their passage through the aluminium, the value of &
must also diminish with the thickness, and thus cause a de-
parture from the predicted form. The last column of Table II
Mr Crowther, On the Transmission of B-rays. 455
gives the values of «log (1 —J/I,) which is proportional to k, and
it will be seen that this product does diminish for the thicker sheets.
On the whole the agreement between the experimental results
and the theory is even closer than might have been expected, but
it is evident that the phenomena of absorption are too complicated
to afford any rigorous test of the theory. Experiments are now
being made along other lines in order to determine this point.
It will be seen that the curve differs from those given by
Wilson in his paper, mainly in the initial portion. His curves
show the final bending round along the z-axis, though he seems
inclined to ascribe it to experimental imperfections. It seems
possible that the greater width of his apertures (1'2 cms. as com-
pared with 0°5 cm. in these experiments) and the fact that the rays
fell upon the absorbing sheets over a fairly considerable angle
instead of in a nearly parallel pencil, caused a kind of general
levelling out, and thus obscured the initial point of inflection of
the curves.
If now we turn to the absorption curves for platinum, we find
an entirely different law of absorption. An examination of the
dotted curve in fig. 6, representing the relation between log I/J,
and the thickness of the absorbing layer, will show that, except
for a slight initial steepening, the curve may be represented by
a straight line to an accuracy well within the probable errors of
experiment. On the other hand the lower curve, giving the
values of I/I,, does not show the slightest approximation to a
linear law. In fact the absorption of homogeneous #-rays by
platinum follows exactly the same law as the absorption by plati-
num of the 8-rays from a single radio-active substance, that is it
is exponential.
The velocity of the -rays used in these experiments was
2°77 x 10” cms, per second. The mean velocity of the B-rays from
uranium X, according to the measurements of H. W. Schmidt*,
is 2°79 x 10” cm/sec. The homogeneous rays used in these
experiments had therefore practically the same velocity as the
rays used in previous experiments in the absorption of the @-rays
from uranium+. The value of X/p for platinum (where X is the
coefficient of absorption assuming the exponential law and p the
density) found from the present experiments is 11:9; the value
obtained with the uranium rays was 9°4 Considering the very
ae nature of the two experiments the agreement is fairly
close.
This result must undoubtedly be ascribed to some secondary
radiation excited in the platinum by the incident rays. We have
already seen that the rays emerging from platinum betray an
* H. W. Schmidt, Le Radium, Vol. v1. 1909, p. 5.
+ J. A. Crowther, Phil. Mag. Vol. x11. 1906, p. 379.
456 Mr Crowther, On the Transmission of B-rays.
entirely different character to those emerging from aluminium
when studied in a second magnetic field. While the latter are
gradually reduced in velocity without any appreciable dispersion
of their velocities about the mean, the former seem to possess
a very considerable range of velocities. It may be noted that
McClelland* has shown that the return @-radiation from any
radiator may be divided into two parts, which differ in their
penetrating power and in their law of distribution. One has
practically the same penetrating power as the primary #-rays,
and is probably purely scattered radiation; the second type is
less penetrating and is probably a true secondary radiation. The
former is the predominating factor in elements of low atomic
weight such as aluminium, while the latter predominates in
elements of high atomic weight such as lead or platinum.
It seems, therefore, that the first stage in the absorption of a
beam of homogeneous 8-rays by platinum is their transformation
into secondary radiation (during the initial steeper portion of
the curve). The absorption of these secondary rays in the further
sheets of platinum then takes place according to an exponential
law. The rapidity of this conversion, which seems to be complete
in 0°001 cm. of platinum, is at first somewhat startling. It is,
however, quite in accordance with previous experiments} on the
scattering of the @-rays from uranium, which may be regarded
as showing that the distribution of the 8-rays in a sheet of gold
reaches its final form in a thickness of little more than 0:0002 cm.
It is interesting to notice that Sadlert has very recently
shown that the absorption of the secondary corpuscular radiation
emitted from different radiators under the action of homogeneous
secondary Réntgen rays is also absorbed according to an expo-
nential law.
We are thus led to the following result. When §-rays are
emitted by any substance, whether due to its own radio-active pro-
perties, or excited by external radiation of a single definite type,
the absorption of the rays emitted follows an exponential law.
On the other hand the absorption of a homogeneous beam of
§-rays by a substance such as aluminium which does not emit
any large amount of true secondary radiation of its own, follows
a law the precise nature of which remains to be determined, but
which is certainly not exponential.
If this is so, it follows, as Wilson has already suggested, that
the rays from a single radio-active substance are absorbed accord-
ing to an exponential law by virtue of some special distribution
of velocities in the emergent beam. The results obtained in the
* J. A. McClelland, Proc. Roy. Soc. A, Vol. uxxx. p. 501.
+ J. A. Crowther, Proc. Roy. Soc. A, Vol. uxxx. p. 187.
+ C. A. Sadler, Phil. Mag. March 1910.
Mr Crowther, On the Transmission of B-rays. 457
present paper on the absorption by platinum, and the results of
Sadler already alluded to, on the absorption of secondary cor-
puscular radiation, show that if this is the case a similar distri-
bution of velocities occurs also when secondary §-rays are emitted
under the influence either of homogeneous B-rays or of homoge-
neous Réntgen rays; while the experiments of Schmidt, described
in the earlier part of this paper, show that this distribution is
not disturbed during the passage of the rays through very con-
siderable thicknesses of absorbing material.
A law so fundamental, applying equally to the emission of
B-rays under radio-active disintegrations, under the action of
homogeneous §-radiation, and under the action of homogeneous
Rontgen rays, should be capable of some simple explanation in
terms of the properties of the B-rays and of the atom. Until
further experiments have been performed however it seems pre-
mature to frame any suggestion as to its cause, or even as to
its precise nature. A knowledge of the true law of absorption
of homogeneous rays would enable us to determine the initial
distribution of velocities necessary to produce an exponential law
of absorption, and Wilson, assuming that the law of absorption is
linear, has calculated one such possible distribution. No theoretical
evidence in favour of the distribution which he arrived at has yet
been given, and the results of the present experiments seem to
show that the “linear law” of absorption is only an approximation
even for aluminium, and is probably the result of an interaction
of the different causes producing and influencing the absorption
rather than a fundamental law.
One fact alone seems perfectly clear. The absorption of the
B-rays is a far more complicated phenomenon and is influenced
by a far greater variety of causes than had previously been
‘imagined. It is only by disentangling the different phenomena
involved and considering each of them separately that we shall
arrive at any satisfactory idea as to the nature of the processes
involved.
Summary.
Experiments have been made on the velocity of a beam of
homogeneous §-rays before and after their passage through an
absorbing medium. It was found that aluminium caused a small
but perceptible diminution in velocity of the rays, without any
appreciable disturbance of the homogeneity of the beam. On the
other hand a homogeneous beam of 8-rays after passing through
platinum emerged with a fairly wide range of velocities.
458 Mr Crowther, On the Transmission of B-rays.
The absorption of a parallel pencil of homogeneous B-rays by
aluminium and platinum has been determined. The absorption
curve for aluminium is complicated, being neither “exponential”
nor “linear.” It approximates, however, to a form very recently
suggested by Prof. Sir J. J. Thomson. The absorption curve for
platinum after a steeper initial portion is exponential. This
result 1s assigned to secondary radiation.
I take this opportunity of again expressing my best thanks to
Prof. Sir J. J. Thomson for much kindly interest and many
helpful suggestions.
Mr Lusby, Some Experiments on Ionisation in Dried Air, 459
Some Experiments on Ionisation in Dried Air. By 8S. G.
Luspy, Emmanuel College. (Communicated by Professor Sir
J. J. Thomson.)
[Read 14 March 1910.]
(1) Introduction. In examining the physical properties of
ions, one cannot help being struck by the important part which
moisture plays in the determination of the coefficie.ts which
define these properties.
For example, in moist air, the coefficient of diffusion of positive
ions is ‘032, and that of negative ions is ‘035. If, however, the
gas be dried, the coefficient for positive ions drops to -028, whilst
in the case of negative ions there is a large increase to ‘043.
Under certain conditions one can take advantage of this difference
in the rates of diffusion between the two kinds of ions and com-
municate a decided positive charge to the gas.
Again, the velocities of ions in any gas are affected if the gas
be allowed to retain any moisture; for example, in moist air, the
velocity of the positive ion under a potential gradient of 1 volt
per centimetre is 137 centimetres per second, for the negative
ion 1°51; if the air be dried, the velocity of the positive ion is
changed very slightly to 1:36, whilst that of the negative ion rises
to 1:87.
In both sets of measurements it is seen that the action of
‘drying the gas is more pronounced in its effect on the negative
ion, but it should be remembered that the positive ion is also
affected, though in a lesser degree. Air does not show this latter
modification very well—probably on account of its complex struc-
ture—but in other gases, e.g. oxygen, hydrogen, and carbon dioxide,
the effect is very marked, as is seen by studying any standard
tables of coefficients.
In condensation experiments this difference in the action of
positive and negative ions is again noticeable ; each kind of ion has
its own condensation point. The experiments of C. 'T. R. Wilson*
have shown that when the ratio of expansion of a gas is 1°25,
condensation occurs round negative ions, but not till the ratio is
increased to 1:31 do the positive ions produce a condensation
cloud. This suggests that the negative ions act more readily
than the positive ions as nuclei for the condensation of water
vapour.
All these facts point to the conclusion that the negative ion is
much more intimately connected with water vapour than the
positive, and it was thought that if by some means an ionised gas
* C. T. R. Wilson, Phil. Trans. A, cxcitt. 1899, p. 289.
460 Mr Lusby, Some Experiments on
could be thoroughly dried, then it should acquire a strong positive
charge. The present paper gives an account of some experiments
made to try and detect such an action in air.
(2) Haperimental conditions. The problem was first attacked
directly. A stream of undried, unfiltered air was drawn through
brass tubing by means of a water pump at an approximate rate of
50 cubic centimetres per second. Near the end of the apparatus
where the air entered was a roll of filter paper, 1 decimetre long,
on which uranium oxide had been fixed by means of acetyl
collodion: this served as the ionising agent. The ionised air then
passed through a copper U-tube, which could be surrounded by
liquid air, and then passed into a Faraday cylinder which was
connected to a Wilson electroscope of ordinary type—a sensitive-
ness of 60 divisions per volt being generally employed. In order
to avoid diffusion effects as far as possible, the brass piping was
chosen with a fairly large diameter (4 centimetres); the U-tube
was necessarily smaller, being only 1°5 centimetres in diameter,
and the total length immersed in liquid air was about 15 centi-
metres. Liquid air was chosen as the drying agent in order to
make the action as perfect as possible; this method has the
further advantage that it does not cause any mechanical filtering
effect such as the use of calcium chloride or sulphuric pumice
might produce.
The experiment consisted in merely placing a cylinder of
liquid air round the U-tube and testing the electroscope for
charge. In no case could any charge be detected, even though
the electroscope’s sensitiveness was pushed as high as 80 divisions
per volt; special care was of course taken to render all insulations
perfect.
To further test the matter, the Faraday cylinder was replaced
by a condenser of the type used by Zeleny and other workers with
blast methods, so that the positive and negative charges could be
measured separately and compared, by raising the outer wall of
the condenser to an appropriate positive or negative potential
whilst the mner electrode was connected to the electroscope. The
diameter of the outer brass tube of the condenser was 4 centi-
metres, that of the inner electrode 7 millimetres, and the total
length was 15 centimetres; a potential was applied sufficient to
drive on the imner electrode all ions whose mobilities exceeded
1 centimetre per second. In order to avoid effects due to the
charging up of the ebonite insulation, the air was made to enter
and leave the condenser through earthed tubes.
On measuring the positive and negative charges in the dried
air blast, a surprisimg phenomenon manifested itself; the two
charges were exactly equal, but were two or three times the
corresponding quantities in the undried air, Results were variable
Tonisation in Dried Arr. 461
from day to day, but in no case was the ratio of increase less
than 2.
At first, it was thought that this effect might be due to the
low temperature and dependent upon the metal of which the
U-tube was composed. The copper tube was therefore replaced
by a glass one of approximately the same section, and the experi-
ment was repeated—but without any change in the result.
The uranium oxide, the ionising agent, was then suspected ;
if it gave off an active gas which condensed at the low temperature
of liquid air, the results obtained might perhaps be explicable.
Obviously this action could be eliminated by employing another
ionising agent. The simplest that suggested itself was the natural
ionisation of the air. It is well known that under normal con-
ditions there is present in the atmosphere a quantity of radium
emanation sufficient continually to produce small ions of both
signs at the approximate rate of 30 per cubic centimetre. This
gave a small but fairly constant source of ionisation to work on.
Here again, the drying (or cooling) of the air almost trebled the
ionisation, and the uranium was restored to its place.
The only other possible causes for the phenomenon which
suggested themselves were diffusion, recombination, and conversion
of large ions into small ones.
Diffusion was first tested. As was pointed out in the intro-
ductory section of this paper, the coefficient of diffusion of negative
ions in air is 50°/, greater than that of positive ions, and this
should lead to an excess of positive ions, if conditions were such
as to allow of such action. Although it seemed extremely unlikely
that the large tubing used could account for the effect, the matter
was tested directly. U-tubes of two different bores, one greater
and one smaller than that originally used were inserted, but with-
out any appreciable change in the result.
The question of conversion of large ions into small ones
promised to give an explanation of the phenomenon. These
large ions, discovered by Langevin* in 1905, have a mobility
of only 3 x 10-4 centimetres per second and occur naturally in the
atmosphere, there being normally about 2000 of each sign in a
cubic centimetre of air. The dimensions of the testing apparatus
were such that only a negligibly small portion of them were
caught. In a recently published paper, M. de Brogliet has shown
that these large ions are produced by the combination of ordinary
small ions (whose dimensions are of molecular order) with large
“neutral centres,’ whose linear dimensions are 100 times that
of a molecule, that is about the size of ultra-microscopic particles
or particles suspended in colloidal solutions, namely about 10 py.
* Langevin, C. R. cxu. 1905, p. 232.
+ de Broglie, Journ. de Phys. Dec. 1909.
VOL. XV. PT. V. 30
462 Mr Lusby, Some Experiments on
M. de Broglie has further given a general method for detecting
and controlling these nuclei. If by the action of drying, some of
these large ions were broken up into a small charged portion and
a large neutral system, the small portion would be caught by the
te sting condenser and give an effect of the nature observed. This
type of analysis of the large ion, viz. into one charged and one
neutral portion, is the only one admissible if we assume that the
ion possesses only one electronic unit of charge and further assume
that this unit is indivisible; the latter supposition seems to
be supported by experiment, but the former is as yet purely
gratuitous.
To test this theory, the air before entering the apparatus was
deprived of all its 1ons—large and small—by passing through
a long condenser charged to an appropriate potential. Small ions
are quickly produced spontaneously, but it takes a fairly long time
for these to combine with the neutral centres to form large ions.
In some previous experiments carried out by the writer*, it was
found that air thus deprived of large ions did not again acquire
the normal number till after about 20 minutes; de Broglie
(loc. cit.) has investigated a similar effect, and states that it
requires a considerable time for the large ions to attain their
maximum number, but gives no exact figures. As the time
required for the air to pass from the electrical filter to the U-tube
is at the most only 5 seconds, one seems justified in concluding
that no appreciable reproduction of large ions occurs in this interval.
On trying the above experiment, it was found that the result was
quite independent of the large ions present in the air.
There now remained only the question of recombination, which
however did not promise to give a solution of the problem; for
recent work by Erikson} has shown that the coefficient of recom-
bination increases as the temperature decreases, which obviously
would give an effect entirely opposed to that observed. It is true
that the coefficient thus found was under conditions of constant
density, whereas in the present investigation conditions of constant
pressure obtained. Still one could roughly suit the constant
density coefficient thus found to the present case (where the
pressure at any temperature would be higher) by superposing on
it conditions of increased pressure. Now, according to M°Clung?,
the coefficient of recombination is independent of pressure between
the limits of 0°1 and 3 atmospheres; whilst Langevin§ showed
that below these limits the coefficient decreases rapidly as the
pressure is lowered. Thus an increase of pressure would in the
* Lusby, Journ. Roy. Soc. N. S. W. June 1909.
+ Erikson, Phil. Mag. Aug. 1909.
+ MeClung, Phil. Mag. March 1902.
§ Langevin, C. R. cxxxtv. 1902, p. 646.
Tonisation in Dried Arr. 463
former case not affect Erikson’s coefficient at any temperature and
in the latter case would increase it. In either case, the effect
of temperature on recombination would give a result quite the
opposite to that observed. Still, in order to verify this theory,
the position of the ionising agent was altered, and it was placed
between the U-tube and the testing condenser. Obviously, if
recombination were causing the phenomenon, the current received
by the electroscope would depend on the distance between the
uranium and the testing condenser. The result was surprising ;
the ionisation in the dried air was increased to 10 times that in
ordinary air, instead of only twice, as before. This seemed to
point to the fact that reduced recombination occurred in the dried
air, although I am not aware that any previous experimenter
ever suspected or allowed for this action. To make sure of the
point, the air before entering the apparatus was passed first
through a tube 3 decimetres long, containing calcium chloride,
and then through another tube 4 decimetres long, containing
pumice, which had previously been treated with sulphuric acid
in the ordinary way. On immersing the U-tube in liquid air as
before the ionisation was still increased tenfold, and the negative
action of water vapour on recombination confirmed.
The only other thing that remained to be tried was the effect
of dust. All early experimenters on recombination found that, in
order to obtain consistent results, dust must be carefully excluded
from the gas experimented on—a result clearly illustrated by
Owens’* experiments with tobacco smoke. Although it seemed
extremely improbable that drying (or cooling) a gas could remove
its dust particles, still the result of filtering the air was tried.
At first, only a decimetre of cotton wool was used, with the result
that, on drying the air as before, the increase in ionisation was
only about 100°/,; when the length of cotton wool was increased
to 5 decimetres the phenomenon vanished altogether, and was
therefore due solely to recombination.
(3) Discussion of Results. The negative result obtained in
the primary investigation, namely the absence of any preponder-
ance of charge of one sign in dried air, is certainly disappointing.
As was pointed out earlier, practically all the known properties
of ions are modified by water vapour, such modification being
more pronounced in the case of negative ions; still one must not
forget that the positive ion is also affected by moisture, though to
a lesser degree. It may be objected that the effect sought for is
masked by the recombination effect; but that is not so, for in the
first method employed the electroscope was quite sensitive enough
to easily record a 5 °/, difference between the two charges. Further,
* Owens, Phil. Mag. Oct. 1899,
30—2
464 Mr Lusby, Some Experiments on Ionisation in Dried Air.
in the very last experiment carried out—namely, that with filtered
air—the effect of drying alone was tested, and neither the positive
nor the negative charge was affected. This result shows that
either the ions go through the U-tube intact, or else they drop
their water molecules and pass on; and their mobilities in the
latter case being presumably those they would possess in dry air,
they are still caught by the testing condenser.
The secondary effect, accidentally discovered, is in some ways
more interesting than the main result, on account of the light
which it seems to throw on the nature of the large neutral centres
in the air, investigated recently by de Broglie (Joc. cit.). In the
atmosphere there are normally present three types of bodies which
are of importance in an ionisation theory, viz. small ions, neutral
centres, and large ions, the latter being a combination product
of the two former. When a gas Is in statistical equilibrium, some
of the small ions are constantly combining with small ions of
opposite sign, others combine with neutral nuclei to form large
ions, and a proportion of these large ions combine with large ions
of opposite sign. Here two main coefficients of recombination
have to be considered, that of small ion with small ion, and that
of small ion with large ion. Now, other things being equal, the
coefficient of recombination between two ions depends on the sum
of their mobilities, hence the former coefficient is approximately
twice the latter. But as the large ions outnumber the small ones
by 50 to 1, the chief factor in recombination is the large ion;
or—to go back one step—the neutral centre. Hence anything
that removes these large nuclei will tend to reduce recombination ;
this is the present-day method of accounting for the action of
so-called “dust.” As to what happens to these nuclei at the
temperature of liquid air one can only speculate. They must
either be deposited in the U-tube or else dissociate into smaller
bodies, whose chances of combining with a small ion are rare.
de Broglie (loc. cit.) states that high temperatures break up
the nuclei; it is reasonable to suppose that a low temperature
could do the same. If we supposed them to consist partly of solid
and partly of gaseous matter, then the great difference in the
coefficients of expansion of the different constituents could con-
ceivably break up the complex system at a low temperature, on
the same principle that damp rocks crack in cold weather. It is
important to note that water plays no part in this action; the
effect occurs equally well in dry or damp air. Whatever may be
the composition of the neutral centre (and therefore of the large
ion) evidently water is not present to any large extent.
In conclusion, I wish to thank Prof. Sir J. J. Thomson for his
valuable suggestions and kindly interest during these experi-
ments.
Professor Thomson, On the Scattering etc. 465
On the Scattering of rapidly moving Electrified Particles. By
Sir J. J. THomson, Cavendish Professor of Experimental Physics.
[Read 21 February, 1910.]}
When rapidly moving electrified particles pass through matter,
each particle as it passes through an atom of the substance, or
perhaps even when it passes close to such an atom, is deflected.
The amount of the deflection will vary with the way the par-
ticle strikes the atom; there will, however, be a mean value
for the deflection produced by an atom on the direction of
motion of a particle passing through it, and when we are con-
sidering only the effects produced by large collections of particles
we may suppose that the path of each particle suffers the mean
deflection. The direction of this deflection is quite arbitrary.
Let us consider now the case when a large number of particles
pass through a large number of atoms and consider what would
be the average deflection of the particles after they have passed
through m atoms. Since the direction of the deflections are quite
arbitrary, it 1s evident that the problem is the same as that of
finding the average value of the resultant of n displacements of
arbitrary phase and of constant amplitude @; if @ is the average
deflection of a particle passing through an atom. This average
value is known (see Lord Rayleigh, Theory of Sound, 2nd Edition,
Vol. I, p. 35) to be Vn.0@. Thus if the electrified particles are
corpuscles moving normally through a plate of thickness ¢, then
if there are NV atoms per unit volume of the plate, and if b is the
radius of an atom, the number of atoms traversed by a particle
on its journey through the plate is N7b?t, and hence the mean
value of the deflection experienced by a particle when passing
through the plate is V Nab?t. 0.
This supposes that the particle is not bent so much in passing
through the plate that the length of its path is materially
different from t.
We shall now proceed to calculate the value of 0.
Regarding the atom as consisting of NV, negative corpuscles,
accompanied by an equal quantity of positive electricity, the
deflection a negatively electrified particle experiences when
passing through the atom arises from two causes. (1) The
repulsion of the corpuscles distributed through the atom, and
(2) the attraction of the positive electricity in the atom.
The amount of deflection due to (2) will depend upon whether
the positive electricity is uniformly distributed through the atom,
466 Professor Thomson, On the Scattering of
or whether it is supposed to be divided into equal units, each
occupying a finite volume probably much greater than the volume
occupied by a corpuscle.
We shall calculate the deflections due to the negative and
positive charges separately. Let us take that due to the cor-
puscles first. We can show easily by the theory of forces varying
inversely as the square of the distance that when the moving
particle is travelling so rapidly that its deflection is small, this
deflection is equal to
2e? 1
mV? a’
when V is the velocity of the particle, e its charge, m its mass,
and « the perpendicular let fall from the corpuscle on the direction
of motion of the particle. Thus the mean value of the deflection
produced by the corpuscles which are within a distance a of the
line of motion of the particle, supposing the corpuscle uniformly
distributed is
4e? 1
mV? a
Now if the length of the path of the particle in the atom is J,
the number of collisions between the particle and the corpuscles
within a distance a from its path is, when the corpuscles are
uniformly distributed, nza*l, when n is the number of corpuscles
per unit volume of the atom; hence by the theory of probability
the average value of the total deflection of the corpuscle when
passing through the atom is
4e? 1
mv? a
4e?
=— ,/
ame nl,
Vnca2l
Now if b is the radius of the atom, the mean value of VJ is
4/2b. Hence 0, the mean deflection of the particle due to the
corpuscles in the atom is given by the equation
e ey
8, 5 mv? ie
AO ae 2
5 mo?b “9°
where JV, is the number of corpuscles in the atom.
Let us now take the case of the positive electricity, let , be
the average deflection when the positive electricity amounting
rapidly moving Electrified Particles. 467
to N,e is supposed to be uniformly distributed through the sphere
of radius b, then it is easy to prove that when ¢, is small it is
given by the equation
When the positive electricity is made up of definite units 0,
the mean deflection due to these is given by the equation
16 2 1 eM ei
ee ee Oasis
2 V1-(1 ae
5 mud
where o is the ratio of the volume occupied by the positive
electricity to the volume of the atom.
The mean deflection 6 due to both negative and positive
particles will be
b=
(2+ pi}? or (8+ b:'}%
according as we take the first or second hypothesis.
The average deflection when passing through a thin plate
whose thickness is ¢ is VNarb?t.0, and substituting the values
of 6, we find for this quantity
e (384 Tee Naty ee
cag gg Mot 7 Wat / Neat
@ [384 T\ ) Pow
according as we suppose the positive electricity to be uniformly
distributed through the atom or done up into separate units.
As these expressions contain no unknown factors beyond N,,
the number of corpuscles in an atom, they indicate that ex-
periments on the scattering of light by very thin plates afford
a simple method of determining the number of corpuscles in the
atom. In making these experiments it is necessary to remember
that we have supposed the deflection small so that the length
of path was equal to the thickness of the plate, and secondly we
have supposed that the velocity remained unchanged; as the
deflection varies rapidly with the velocity this condition is im-
portant, and it is the more so because the expressions for the
change in the velocity of the corpuscle produced by collision with
an atom are (see Discharge of Electricity through Gases, 2nd
Edition, p. 378) much more complicated than those for the de-
flection, they involve other quantities besides the number of
corpuscles in the atom and thus are not suitable for measuring
that quantity. I am not aware of any experiments made quite
468 Professor Thomson, On the Scattering of
under the conditions contemplated in equations A, but such are
now being made by Mr Crowther at the Cavendish Laboratory.
The observations we have are, however, sufficient to show that
NV, is of the same order as the atomic weight of the atom.
' We see from equations A that when the deflection is small
the thickness of the layer of a substance required to produce
a given deflection varies as
Te be ak 385
&\ VN eee iG = ° |
meVe 1 BF [pe net )
- e NN, 25 \- ( 37)
according as the positive electricity is uniformly distributed
through the atom or collected into separate units. We can
show that this result is true even when the deflection is not
small provided the velocity of the particles remains unaltered.
For let f(z, 6) x @ be the fraction of the particles which at a
distance z from the point of projection, measured parallel to the
original direction of projection, have a deflection ¢, where ¢ is
between m@ and (m+1)8@.
Let d be the mean free path of a particle, then f(z + A cos , m@)
will be got from those particles which at a distance z had
deflections (m—1)6@ or (m+1)@; each of these particles will
have made another collision, and if they are equally likely to
be deflected in one direction as the opposite, we see that
F(e+reos 6, m0) =4 f {z,(m—1)O}+43f fz, (mt 1) 4,
(compare Lord Rayleigh, Theory of Sound, vol. 1. p. 35).
Expanding by Taylor's Theorem we get
ey oe CEE
Deli irae
ul cig A) ee.
hence if we put = ie
we have cos $a a =4 ae
an equation which determines / as a function of z’ and ¢. Since
the same value of z’ will give the same value of ¢, it follows that
rapidly moving Electrified Particles. 469
layers of different substances will produce the same deflection if
aa we see
that this implies that the results expressed by equations B are
true even when the deflections are not small.
In the preceding investigation we have supposed that the
angular deflections were all in one plane, the differential equation
satisfied by f(z,¢) when the deflections take place in any plane
may be found as follows :
As before the particles for which z=z+2cos¢, and ¢=¢,
must have come from the particles determined by z and ¢, where
cos d, = cos ¢, cos 8 + sin ¢, sin @ cos y,......... (1)
their thicknesses are proportional to \/@; since \ =
ar is the angle which the plane in which the deflection
takes place makes with the plane through the original direction
of the particle and its direction just before it experiences the
deflection @. As all directions of w are equally probable the
probability of y being between W and w+dywW is dw/zr.
Hence,
dy
FS (z+ Xcoos ¢, dr) =|~ re, fo);
by Taylor’s Theorem, the right-hand side is equal to
Seb) + ag F (eb) |S (e—$)
TAG) a ee SE
From equation (1) we get
2 — $: = 9 cos — 4 G cot g, sin? ,
substituting this value of ¢,—¢, in equation (2) we get
4n df Ll df asf
BF desing dp * cos $ dg
or if cos @ =1, the equation may be written
4ndf 1l-#?df
Paz © to). dt?
or with the same notation as before,
4 ler as
a2) SB dP
or
470 Professor Thomson, On the Scattering of
The conclusions drawn when the deflections were all in one
plane may thus be extended to the more general case.
Although as yet we have no experiments in which the
arrangements have been such as to admit of an accurate applica-
tion of the formulae obtained in this paper, we have data by
which we can calculate the order of the quantity NV, the number
of corpuscles in an atom.
Let us find the path of a particle which moves so that its
deflection is equal to the average deflection for the number of
collisions made by the particle, 7e. if @ is the angle through
which the direction of the particle is deflected, n the number of
collisions made by the particle
b=Vn0.
If s is the length of path travelled by the particle, X the
mean free path n = s/n, and ¢?= s/n.
If x is the distance, measured parallel to the direction of
projection, travelled by the particle
cos d,
or since S= a
de = cos $,¢.dd,
or w= (gsin 6 + cos 6-1},
so that when ¢ = 7/2, or the particle is bent at right angles to
the direction of projection,
w= (m2),
when a is greater than this the particle will begin to travel back
again, hence this value of z must be comparable with the distance
at which the number of particles crossing a plane at right angles
to the direction of projection is reduced to one half of those
projected.
Substituting the value of \/@ previously found we get
mvs 25
e*Na = a
384, 2 -(1-§) a]
‘if we take the second of equations (B),
putting e/m=5:1 x 10",e=5 x10, v=10", N=2 x 3x 10%,
£ = (m7 — 2)
rapidly moving Electrified Particles. 471
we find that for any gas at atmospheric pressure when the
particles have this velocity
50
L=(7 — 2) xX ———————_ roughly.
M, {2 — (1 - Fat
Becker found that cathode rays of about this velocity travel
through about ‘5cm. of oxygen before the number moving
forwards is reduced to 4. Putting c=4 we get for VN, about 50,
if the number of corpuscles were equal to the atomic weight
NV, would be equal to 16. Thus these experiments show that the
number of corpuscles in the atom is of the same order as the
atomic weight; we must, however, wait for experiments made on
different lines before we can determine the exact relation between
the number of corpuscles and the atomic weight.
472 Mr Dixon, Jacobi’s double-residue theorem
Jacobi’s double-residue theorem in relation to the theory of
point-groups. By A. C. Dixon, Sec.D., F.R.S., Trinity College.
[Read 23 May, 1910.]
In this paper I have shewn how Jacobi’s theorem leads
directly to the chief general propositions of the theory of point-
groups in a plane, and have also given a discussion of a converse
theorem. No account has been taken of coincidences among the
points of a group.
1. Jacobi’s theorem is as follows. Let wu, v, w he three
polynomials in two variables 2, y, of degrees m, n, m+n—3
0 (u, V)
0(#,y)
of intersection of the curves w=0, v=0 are all distinct and at
finite distance from the origin, and are denoted by (2,, y,) (r=1,
2... mn), then
respectively, and let J be the Jacobian If the mn points
SG yas 10 (1).
rT=1
(See for instance Netto, Vorlesungen iiber Algebra, vol. 1,
pp. 165—173.)
The following proof is a modification of one given by Netto,
after Kronecker.
If w is an arbitrary polynomial of degree m +n — 8, it contains
4(m+n—1) (m+n-— 2) arbitrary coefficients, and if w is re-
stricted by being supposed to vanish at (a, y,) (r=1, 2... mn),
this number of coefficients is brought down to
4 (m+n—1)(m+n—2)—mn
or 4 (m—1) (m— 2) +4(n—-1) (n—-2)-1
if all the conditions w (#,, y,)=0, to be satisfied by those co-
efficients, are independent, that is, unless there is some relation
> A, w (a, Yr) =0
satisfied by all polynomials w of the degree m+n — 3.
Now if ¢, # are any polynomials of the degrees n — 3, m—3,
Up +o
is of the degree m+n-—3 and vanishes at the mn points, and
contains 4 (m—1) (m—2)+4(n—1) (n—2) arbitrary coefficients,
namely those in ¢ and yw, these being all effective unless for some
set of coefficients ud + vw is identically zero, that is, unless u, v
m relation to the theory of point-groups. 473
have a common factor*; which is contrary to the supposition that
the curves u=0, v=0 meet in mn isolated points.
There must then be a relation of the form
Se ay On se (2),
r=1
satisfied by an arbitrary polynomial w of degree m+n-—3.
The coefficients A can be found by constructing certain
particular polynomials by Kronecker’s method.
* There is a slight difference in the argument at this point when the number of
variables is greater than two. Suppose for instance there to be three variables
X14, T2, T3 and u,, Ug, Uz to be polynomials of degrees m,, mz, m3 and w to be of
degree m;+m,+m3-— 4, so that Jacobi’s theorem becomes
Sw | Firsts 48),
d (1; v2, 23)
It is possible to have polynomials ¢,, ¢2, 3 of degrees mz+m3—4, m3+m,—4,
m, +m, —4, such that
Uy 1 + Ube + U3h3= 0.
Using a bar to distinguish the terms of highest degree we have
Ui, Gi + Uns + Ush3=0,
a homogeneous relation. It is supposed that the surfaces u,, uy, uz have no
common point at infinity, and hence when u2.=0 and u%3;=0, w cannot vanish, so
that ¢;=0. Thus by Néther’s theorem (§ 7 below)
$1= ays — Uso,
where 2, 3 are of degrees mz—4, m3—4 and homogeneous. It follows that
Uz (2+ Uys) + Us ($3 — Wyo) = 0,
and that d= Pus — Pst )
$3= Potty — Pita,
where ¥; is homogeneous of degree m,— 4.
Hence in the identity
U1 + Ugh: + Ush3=0,
$1, $2, $3 may be replaced by the polynomials of lower degrees,
gi—Up3+Usy2, d2—Usyitmps, $3— mot Uy,
and the degrees of these may be lowered similarly until we arrive at the result
$1 = Usps — Uzsh2, d2=UzsY1 — WY3, P3=WY2— U1,
where 4, W2, 3 are of the degrees m,—4, my—4, m3 —4.
Thus if ¢1, 2, ¢3 are arbitrary polynomials of their degrees the effective number
of arbitrary coefficients in
Ujp1 + Urbs + Ushs
is the number of coefficients in $1, ¢2, ¢3 diminished by the number in yy, yo, Ws,
that is,
$ [(mz + mz — 1) (me + mz — 2) (mg + mg —3) + (m3 + my — 1) (ms +m, — 2) (m3 +m, — 3)
+ (my + Mz — 1) (my + mg — 2) (my + mz — 3) — (my — 1) (my — 2) (my — 3)
— (mz —1) (mz — 2) (mg — 3) — (mg — 1) (m3 — 2) (m3 — 8)],
or & (my + Mz + mz — 1) (my + mg + mz — 2) (my + m2 + m3 — 3) — mymgm3 +1.
47 4, Mr Dixon, Jacobi’s double-residue theorem
Since ay? — EPn? = (a? — EP) y1 + (yX— 72) EP, the sum of two
terms which contain the factors «—&, y—7 respectively, we have,
taking the terms of w separately,
u(x, y)—u (E, 9) = Uy (@— €) + U, (yr) eee (3)
where U,, U, are polynomials of degree m—1 in a, y, &, , and
when «=€ and y=7, U,, U, are equal to the derivatives wy, Ue.
Similarly
v(@, y)—0(& 0) =Vi(@—£) + Vay ma) vce (4)
where V;, V, are of the degree oe in x, y, €&, and reduce to
the derivatives v,, v, when v=&, y=
Let U, V,— U,V,=A (a, y, &, 7), Men. by substituting
Lr, Yrs Us, Ys for x, ¥, &, 7 in (3) (4)
we find A Ge Yr, sy Ys) =0, when r#s, while it =J(#,, Yr),
when r=s. J (@,, Yr) 1s act zero since the curves uw=0, v=0
have only isolated intersections.
Now A(a, y, 2s, ys) — A (a, Y, @, Ys) is of the degree m+n—3
only in a, y, the terms of degree m + n—2 destroying each other.
Hence
mn
> Ay {A (GES Urs Vs, Ys) me A (az; Yr, XV, y)} Fa 0,
Su
that is AgJ (Hs, Ys) — Atd (x2, Yr) = 9.
This holds for all suffixes s, ¢ and therefore the relation (2) is
Dae, Yl (os yp) Os cakec eee eee (1),
which is Jacob's theorem.
2. It follows directly that if w vanishes at mn—J1 of the
intersections of u, v it vanishes at all, or that any curve of degree
(m+n —3) through mn—1 of the intersections of two curves of
degrees m, n passes through all their intersections.
Again, let @ be an r°(r<m-+n—3) vanishing at the first
mn—a of the intersections, and W an arbitrary (m+n—r—3)*.
We may put dy for w and thus we have
ee D (Hrs Yr) W (@r, Yr) |S (@r, Yr) = O,
an equation which includes
4(m+n—r—1)(m+n—r-— 2) equations,
linear in b (Ly, Yr) (r =mn —a+1,... mn),
and therefore gives ¢(2,, y,) = 0 for all these values of r if
a=}(m+n—r—1)(m+n—r—-2),
in relation to the theory of point-groups. AT5
and if all these a equations are independent, that is, unless for
some set of coefficients
he (Lr, Yr) =0(r=mn—atl],... mn).
This is the theorem of Cayley and Bacharach, that a curve of
degree r(< m+n -—2), which passes through all but
4(m+n—r—1)(m4+n-—r-—2)
of the mn intersections of two curves of degrees m, n, passes
through the excepted intersections also unless these excepted
points lie on a curve of degree m+n—r—3. There is no ex-
ception when r=m+n—3.
Similarly in three dimensions, a surface of degree m+n+ p—4,
which passes through all but one of the intersections of three
surfaces of degrees m, n, p, passes through all, and a surface of
lower degree r must pass through all the intersections if it
passes through all but
£(m+n+p—r—1)(m4+n+p—r—2)(m4+n+p—r-83),
unless these excepted points lie on a surface of degree
mt+n+p—r—A.
Bacharach has further noticed that the lowest value of £B,
such that an r° curve ¢ can pass through mn-— 8 of the inter-
section of u, v, say A, without passing through the rest, say B,
is m+n—r—1, and that in such a case the points B are collinear.
For if y is any (m+n —r—3)® we have
SPp/J =0,
the summation being over the @ points B, and thus any
through all but one of these passes through the other. If
B=m+n—-r-—-2,
take yr to consist of straight lines drawn from an arbitrary origin
to all but one of the points B: this composite curve cannot always
pass through the excepted B point, if the B points are distinct.
Thus 8 cannot be less than m+n—r—1.
If B=m+n-—r-—1, suppose B,, B,, B; to be three of the
points B, not in a straight line, and take to consist of the line
BB, and lines joining B,, B;, B,... to an arbitrary origin: this
will not always pass through B;. Hence all the points B must be
collinear.
Also 8 can have this value. For take
uU= Di Si FA pene
V=2n-1 =f; m+n—r—1fr—m+13
A476 Mr Dixon, Jacobi’s double-residue theorem
where fp 18 an arbitrary (m—1)* and so on. Then a form
for $ 18 fna frm — fra fr-nvs: this is an 7° vanishing when-
ever u,v both vanish, except at the m+n—r—1 points where
z= 0, Jm+n—ra = 0.
3. Theorem of Riemann and Roch. Take any qg points (A) on
a curve u=0, of degree m. Through these describe an n‘* curve
v=0(n>m-—83), cutting u=0 in mn—gq other points (B).
Let X be the number of arbitrary coeticients in an n‘* vanishing
at all the points B, and uw the number of arbitrary coefficients in
an (m — 3)* vanishing at all the points A. Then shall
A=$(n4+1) (n+ 2)—mn+qtyh.
For if @, y are of degrees n, m—3 we have
= dy/J =0.
A,B
Suppose ¢@ to vanish at B; then we have here X relations
satisfied by the values of w at A, but among these relations
4(n—m+1)(n—m+2)41
are illusory, namely those given by putting ¢ =v or wy where x
is of degree n—m. The number of relations is thus reduced to
~-—$(n—mM+4+1)(n—m+ 2) —-1,
but it is not less than this, for the number of illusory equations
is the number of linearly independent ni ¢ which vanish at all the
points A, B. Let ¢ be any such, then by a suitable choice of the
constant @ we can make ¢—av vanish at a new point P on u=0
and therefore contain w’ as a factor, wu’ being that factor of wu
which vanishes at P. Thus ¢-—av=wuw’, say. If u=ww’...,
the factors u’, uw”... being of course irreducible and of degrees
m’,m”,... then w is of degree »—m’ and vanishes at the nm”
points where ¢=0 and v=0 meet u”=0. Hence w must contain
w’, and so on for all the other factors. Thus even when w is
composite, the only n** which vanish at all the pomts A, B are
included in the form av + wy.
The values of an arbitrary (m—3)* at the points A are then
connected by
rN—-4(r—mM4+1)(r—m+2)-1
linear relations, and w, the number of arbitrary coefficients in an
(m— 3)* through the qg points A is therefore
>h(m—1)(m—2)—-q+aA—$ (n- m+ 1) (n—m+4 2)—-1,
or U+ mn — (N41) (14 2) —|G...reerecreeees (5).
im relation to the theory of point-groups. 477
Again, in the equation = ¢y/J =0 suppose to vanish at
A,B
the points A. Then w contains pu arbitrary coefficients and thus
the values of any ¢ at the points B are connected by w linear
equations, of which none can be illusory since no w can vanish
at all the mn points A and B. Hence X, the number of arbitrary
coefficients in an n° through the points B,
>4(n+1) (n+2)—mn+q+yp,
that is, be<r+mn—$ (nt 1) (m4 2) —q 6... ee. (6).
Comparing (5), (6), we have the theorem of Riemann and
Roch, that
N=$(n+1)(n+ 2)—mn+q4 pm.
4. It1is important to prove that no other linear relation except
(1) connects the values of an arbitrary (m+n— 3)** at the mn
intersections of u=0, v= 0, that is, that an (m+n—3)'* w can be
found such that
W (Lp, Yr) = Oy (r= 2, 3... mn)
where the mn—1 quantities a, have any values whatever. Such
a polynomial is in fact given by Kronecker’s method of inter-
polation, and is
mn Ay
ZF Cn We)
Hence no other linear relation than (1) connects the values of w
at the mn points, and from the course of the proof in § 1, any w
which vanishes at the mn points must be expressible in the form
ub + vy, where ¢, are polynomials of the degrees n — 3, m— 3.
Two other proofs will now be given of this result, which was
first proved by Nother (Math. Ann. vol. 6, p. 354).
5. In the theorem of Riemann and Roch put m+n — 3 for n
and suppose the points B to be (a,, y,) (r=2,3... mn), so that q
takes the value m(m+n—3)—(mn—1) or m(m—3)+4+1. Thus
no (m— 3) can contain all the points A, and yw takes the value 0,
N=4(m+n—1)(m+n — 2)—(mn—1)=4 (m—1)(m—2)
+4(n—1)(n—-2).
This is exactly the number of arbitrary coefficients in the expres-
sion ud + vy, so that the result follows.
6. For a third proof, apply Jacobi’s theorem to the poly-
nomials (# — &)u, (y— 7) v, w, where & 7 are the coordinates of an
‘arbitrary point.
The points where (#— &)u,(y—7)v both vanish are
(1) The points (#,, y,) and here
0 (a — mC
: soe i. = (@, — €) (Yr — 0) F (Ars Yr)
VOL. XV. PT. V. 31
{(A (2, Y, Ly, Yr) — A (a, Y, X, Y;)}-
478 Mr Dixon, Jacobi’s double-residue theorem
(2) The point (&, 7) where the same Jacobian is equal to wv;
(3) The points (€, Y,) where «= & v=0: at these the Jaco-
bian is equal to u(y — 7) v9;
(4) The points (X,, 7) where y=7, u=O and here the
Jacobian is equal to v (# — &) uy.
Thus substituting x, y for & » we have
0S eS sae sch UE)
wu r=1 (w 77 Ly) (y a: Yr) J (2, Yr) r=1U (x, Y,)( Y, i, y) U2 (@, Y,)
tt w(X,, y)
> = = (ONC:
ia wy (X,,y) (X,— 2) v(X,, y) 7)
and the degree of w may be anything up to m+n—1. We have
to examine the third and fourth terms on the left in (7). As to
the third term, let w/uv be reduced to partial fractions as a
function of y, being treated as parametric. The denominators
of these fractions are y — Y,(r =1, ... n) and the factors of wu.
The fraction whose denominator is y— Y, has for its nume-
rator w («, Y,)/w(x, Y,) v(x, Y,) and the sum of these n fractions,
with sign changed, forms the third term in (7). Let their sum
be brought to a common denominator, v, the numerator will then
be of degree n—1 in y, and its coefficients being symmetrical
in Y,, Y,... Y, will be rational functions of 2, but in general
fractional: let P denote this numerator. Similarly the other
partial fractions will have a sum Q/w, where @ is of degree m — 1
in y, and its coefficients are rational in a,
Thus CTE EE)
UI Oy eh
w= Pu+Qv:
but this identity determines P, Q uniquely if their degrees are
n—1, m—1 in y, unless u,v as functions of y have a common
factor, which 1s only true for special values of z, namely 2}, #...%mn.
Similarly, if #, S are integral in w and of degrees n—1,m—-1
and are such that
w= Ru + S82,
the fourth term in (7) must be — S/u.
Hence (7) becomes
I ee NE ees)
Wi par (@—2,)(Y — YT (&, Yr) VU
and if P is not integral its denominator is a function of # only,
and that of S isa function of y only. These denominators must
in fact be II (w—~,) and II (y—y,).
in relation to the theory of point-groups. 479
If then w (2,, y,) =0, (r=1, 2... mn), we have from (8)
w= Pu+Sv
and P, S can no longer be fractional, since w is not fractional and
the denominators of P, S have no common factor.
Hence any polynomial w of degree <m+n-—1, which
vanishes at (2,, y,) (r=1, 2... mn), must be of the form ud + vw
where @¢, ¥ are polynomials of degrees n — 1, m — 1 respectively.
If w is of degree m+n—2 only, the terms of degree
m+n—1 in up + vy must cancel, which can only happen if the
terms of degrees n — 1, m—1 in @¢, vanish identically, since the
curves u,v have no intersection at infinity. By applying this
argument repeatedly we find that the degrees of $,W are
r—m,r—n where r is that of w.
To extend the theorem to higher values of r than those for
which it has been proved, it is only necessary to note that when
r>m+n— 2, homogeneous polynomials ¢,, yr, of degrees
r—mr—-n
can be found such that the highest terms in wd, + vy, coincide
with those in w, so that by subtraction the degree of w is
reduced; when r=m+n—2, the degree can be reduced by
subtracting ud, + uy, +cJ)*, where the polynomials ¢,, yy, and
the constant ¢ are suitably chosen. By applying Jacobi’s theorem
to the reduced expression w—ud,—vy,—cJ, whose degree is
m+n— 3, we find — mnc = 0, so that c must be zero, if w vanishes
at all the intersections.
8. Converse of Jacobi’s Theorem. Suppose now that mn
points (2, y,) (r=1, 2... mn) are such that, for any polynomial
w of degree m+n —3,
Ph AUN (a tty ONG 5 ten alah na) Pesreabiat | (9),
the coefficients a, being independent of those in w, and let us
investigate whether these mn points are necessarily the complete
intersection of two curves of degrees m, n.
We may also take the conditions involved in (9) in a form in
which they have been discussed by Serret, Sylvester, Clifford and
others, namely
PAPA (ipa Pa pas ae) a ae | (10),
for all values of a, b, c.
Divide the mn points into two groups, A and B, containing
respectively 3m (m+ 3) and $m (2n—m-—3) points. Let % be
the number of independent m vanishing at A and / the
* See for instance Camb. Phil. Proc. vol. 14, p. 389. This step is not necessary
if the proof of § 6 is used.
480 Mr Dixon, Jacobi’s double-residue theorem
number among these that vanish at B also. Let « be the number
of independent (n—3)-ics vanishing at B and & the number
among these that vanish at A also.
If $, y are of the degrees m, n — 3, we have
Sey Dies the) A(t Yr) = OF eee (11),
and by taking ¢@ to vanish at A we have X%—J/ homogeneous
linear relations among the values of w at B. It is here supposed
that none of the coefticients a, a,... vanish. Hence
K>4(n—1) (n—2)—- 4m'(2Qn—m—3)+X—-1...(12),
and similarly by taking y in (11) to vanish at B we have
rN >4(m4+1)(m+2)—3m(m4+3)+K—-k...... (18).
By addition
k+l>4(m—n4+1)(m—n4+2)41......... (14).
Similarly
a+7>4(n—m41)(n—-m4+2)4+1 ......0.. (15),
if 7,7 are the numbers of polynomials of degrees m— 3, n
respectively which vanish at all the points (,, y,). The desired
conclusion can often be deduced from (14) and (15). For instance,
if m =n, so that i=k, j=1, we have 1/52 if k=0; that is, the m*
points are common to two mi’ unless they lie on an (m—8)*,
and similarly in other cases. The relations (14), (15) moreover,
as equalities, are those satisfied in general when the mn points
are the intersections of an mand an n®. Still, this is not the
only possible consequence of the condition (9), as the following
cases shew.
I. Take m=8,n=7, so that there are 56 points, and any
curve of degree 12 through 55 of them contains all. Take 56 of
the intersections of two curves of degrees 5,12. Then any 12%
through 54 of these will contain all, and therefore they will satisfy
two conditions such as (9) and yet will not in general be the
complete intersection of a septimic and an octavic.
II. Take m=n=9, so that there are 81 pomts. Choose
these among the 90 intersections of two curves of degrees 15, 6.
Then a 15 through 80 of them will generally pass through the
other one, and a condition of the form (9) is satisfied, but the
points are not the complete intersection of two nonics.
Thus the converse of Jacobi’s theorem appears to consist in
the statement that (14) (15) follow from (9).
9. If u,v are of the same degree, p+ 1, and p of their inter-
sections are collinear we may take w to be $6 where 6 is the line
containing p intersections and ¢ is an arbitrary (2p — 2)". Then
a relation
Dan OD (ays Uy) = Ol ese eee (16)
in relation to the theory of point-groups. 481
holds among the values of ¢ at the p?+p+1 other intersections,
a, having the value
8 (Xr, Yr)[S (Ls Yr).
This case is rather exceptional, in that u,v are not the only
independent (p + 1)'* through the points involved. We may write
u=bV—eU, v=8W-tU
where U, V, W are p'* and 6,¢, € linear; then eW—€V is an
independent (p+1)* through the p?+p+1 points, and the
equations satisfied by these points are*
| Ue Ve W |\=0 eh a Pes CL7.);
Wor ites Dip |
In applying the converse theorem of §8 to this case it is
convenient to take (16) in the form
La, (aa, + by, + 6)? = 0
and integrate, say with respect to b, Thus
La, (ax, + by, + c)”/y, = a function of a, c only,
which must be homogeneous and of degree 2p—1, and can
therefore be represented by the sum of p terms of the form
B (GE Fee.
We have, then, an identity of the form:
payey (ax, + by, a Cea = 0,
containing p?+2p+1 terms, in p of which y,=0. The theorem
of §8 is therefore applicable, m, n being each =p +1.
* A relation of the same kind as (16) can be found among the points where the
determinants (17) vanish, even when neither row is linear.
482 Prof. Thomson, On the phosphorescence observed ete.
On the phosphorescence observed on the glass of vacuum tubes
when the pressure is not very low. By Sir J. J. THomson, Caven-
dish Professor of Experimental Physics.
[Read 14 March 1910,]
If an electric discharge is sent through a vessel from which
the air is gradually exhausted, at a certain stage of the exhaustion
the whole of the walls of the tube will be found to be phos-
phorescent. This phosphorescence is of quite a different colour
from that produced by the cathode rays and occurs at a much
higher pressure, the pressures at which it is brightest vary with
the dimensions of the vessel and with the gas inside it, but they .
are of the order of 1 mm. of mercury. The colour of the phos-
phorescence with soft soda glass is an olive-green, quite distinct
from the yellowish-green of the phosphorescence due to cathode
rays, with lead glass this phosphorescence begins by being greenish
but gets blue as the pressure diminishes. The following experi-
ments show, I think, that the cause of the phosphorescence is
ultra-violet light produced by the electric discharge. A large
vessel was divided into two parts A and B, separated by an
opaque screen which was perforated with a long narrow channel,
thus if any light were produced in A it would enter B as a fine
pencil. The discharge was sent through A and when the stage
was reached when the walls of A phosphoresced the place where
a pencil going through the channel would strike the walls of B
became phosphorescent with a well-defined spot, a little powdered
millemite placed on the glass greatly increased the brilliancy of
the spot. Various substances were placed in the path of the
pencil, glass was found to be fairly opaque to these rays, although
the amount of phosphorescence produced after the pencil has
passed through a cover slip is quite appreciable, and with care
the pencil can be detected after it has passed through the walls
of a vacuum tube. Quartz 1s much more transparent to the
pencil than glass, and white fluorite than quartz. The refraction
of the pencil by the fluorite was quite marked: a plate of fluorite
with parallel sides supported by a glass rod working in a ground-
glass joint was put in the way of the pencil, as the plate was
rotated the spot of light due to the pencil on the screen moved
backwards and forwards just as a spot due to visible light would
have done.
CONTENTS. |
On the relative velocities of. diffusion. in aqueous ee of rihtdiage and
caesium chlorides. By G. R. MInzs. (Two figs. in Text)
Note om the use of the experimental method described in the a a
paper. By A. V. Hint. (One fig. in Text)
A note on some fossil plants from Nowfoindlend, te E. “A. ‘Novant
ARBER. (Two figs. in Text)
A note on Cardiocarpon compressum, Will. By ‘Mrs E. A . Newent
“ARBER. (Communicated by E. A. Neweit ARBER)
On a new species of Physostoma from the Lower Carboniferous Rooks e
Pettycur (Fife). By W. T. Gorpoy. (Communicated by E. is
308-
40P Se oy
AB ls
465 5 = : |
gre e
NEWELL ARBER) ; : Z ; 2 ; 895
On the relation between the fossil Osmundaceae and the Zygopterideae.
By W. T. Gorpon.. (Communicated. by EH. A» NEwELL ARBER)
“On the occurrence of Schizoneura paradoaa, Schimper and Mougeot, in
the Bunter of Nottingham. e R..D. VERNON. ee
by E. A. NEWELL ARBER) _ : - : . Peres i
Notes on the genus Schizoneura, Schimper and Mavjoot By. L. eS eee.
Wins. (Communicated by E. A. Newent ARBER) . 406-
-On Petrified Plant Remains from the Upper Coal Measures of Brstale ee
By D. G. Linu. (Communicated by E. A, NEwELL ARBER) — 411
On the assimilating tissues of some Coal Measure Plants. | = a a
HamsHaw THoMAsS. .- 3 413
The production of Cathode Davide by ee ee Radi
tions. By R. T. Bearry. (Communicated by Professor Sir J. J. ances
THomson.) (Three figs. in Text) : igs - 416 ,.
The solution of a system of differential equations occurring in the. theory :
of radio-active transformations. By H. BATEMAN. ss fig. in Text) 423_
‘On double-sixes. By W. BURNSIDE : i : : . 498
On the Procession and Pupation of the Larva of ee pinivora. =
By T. G. Epwarps. (Communicated by H. H. Brinpizy)
Secondary Réntgen Rays from Metallic Salts. By J. UL. Guasson. (Com-> Ss
municated by Professor Sir J. J, Tomson.) (Five figs. in Text) . 437 _
On the Transmisnion of B-rays. By J. A. CRowTHER. (Six figs. in Text) 442~
- Some Experiments on Ionisation in Dried Air. By S. G. Luspy. oS ‘
municated by Professor Sir J. J. Tomson) : 459
On the Scattering of rapidly moving a Particles. By Profesor PRR,
Sir J. J. THOMSON j f
Jacobi’s double-residue theorem in Melabion to ee tary ig point groups.
By A. C. Dixon ; : j 5
“On the phosphorescence ena on the glass of vacuum. = hon re
pressure is not very low. By Professor Sir J. J. THoMson
19 482. eg
PROCEEDINGS |
a CAMBRIDGE. PHILOSOPHICAL =
“SOCIETY.
4 VOR Ry ERRT VL
[Easter Term 1910.)
: rae = ae ee
<P ODE AL SiAt sy
men “LOSGPIECAL wi iike 5
— =-OF=-.
; t
7A ? te oe
\? LIN
: Cambridge:
AT. THE UNIVERSITY PRESS,
AND SOLD BY
DEIGHTON, BELL & CO. AND BOWES & BOWES, CAMBRIDGE.
: CAMBRIDGE UNIVERSITY PRESS,
C. F, CLAY, MANAGER, FETTER LANE, LONDON, E.C.
ne 1910. ae
Price Three. Shillings
- 20 October, 1910.
‘NOTICES.
af oe for copie. ects of sie ‘Set ee =
Volumes (in Parts) of the Transactions should be made +0 the
s Secretaries of the Society.
2. Separate copies of certain parts of Pounce pts of ‘die EN
Transactions may be had on ‘application. to Messrs BowEs & es
Bowes or Messrs Deicuton, Butt & Co., Cambridge. is
3: Other volumes ‘of the Pransoctions may be ‘Gbianed at <2:
the following prices: Vol. xu. £1. 10s. 6d.; Vol. xm. $i Qs. 6d-3
_ Vol. x1v. £1. 17s. 6d.; Vol. xv. £1. 12s. 6d. ; Vol. xvi. £1. 10s. 0d. ;
Vol. xvii. £1. 2s. 6d.; Vol. xvii. £1. 1s. 0d.; Vol. XIX. £1. 5s. 0d. ;
Vol. xx. £1. 10s. Od.; Vol. xxi. No. 1, 3/-: No. 2, 4/-; Nos. 3 and j
4, 1/6; Noi? 5: and’ 6 3/-; No.7, 2/-; No. 8, 8/-; No.9, 1/6;
No, 1s 1/6; No. 11, 1/6; No. 12, 2/6; No.18, 1/6; No. 14, 1/6.
de “ Coniplete sets of the Proceedings, Volumes” i--EY, seks
may also be obtained on application to the. > Secretaries: of ‘the AG
Society.
a ain Letters and Communications for. the Society. should be e
aoe to one of the Secretaries, :
Mr A. E, Supiey, Christ's Callenee Se ae
Dr E. W. Barnes, Trinity College. fee :
Mr A. Woop, Emmanuel College. [Physical]
6. Presents for ile Library of the: Soviety should be ad-
dressed to.
The Philosophical Ladi,
New Museums, -
: Cambridge, 2
6 Authors of papers are ifoomed that the Tlustrations at =
. Diagrams are executed as far as possible by photographic “process =
work, so drawings should be on a large scale ee on eee 1 white =
Bristol board in Indian we ;
ao Members of the Souniy are “Yyequested to inform the
oe of any change of address. ee
PROCEEDINGS
OF THE
Cambridge Philosophical Society.
On the Mobihties of the Ions produced in Air by Ultra- Violet
Inght. By A. Lu. Huaues, M.Sc., 1851 Exhibition Research
Scholar, Scholar of Emmanuel College, Cambridge. (Communi-
cated by Professor Sir J. J. Thomson.)
[Read 9 May 1910.]
Since the discovery of the ionisation of gases by X-rays, several
investigations have been made to determine whether there is any
increase in the conductivity of gases when exposed to ultra-violet
light. It is well known that a large current of negative electricity
can be obtained from metallic and other surfaces when ultra-violet
light falls upon them. Yet when the same ultra-violet light is
passed through a gas it is difficult to get evidence of any increased
conductivity. Absorption of ultra-violet light by a gas does not
necessarily mean a corresponding ionisation, as Henry* and
Whiddingtont found for iodine vapour which absorbs ultra-violet
light considerably but shows no increased conductivity due to the
light.
Lenard} carried out some experiments which appeared to show
that air was made conducting under the action of a very absorb-
able kind of ultra-violet light. He determined the mobilities of
the ions so produced, and found for the negative a mobility of
3°13 cm./sec. and for the positive a mobility of ‘0015 cm./sec. The
latter is of quite a different order to the mobilities of ions pro-
duced by X-rays and the radiations from radio active substances.
This led to the suggestion that the positive carrier in Lenard’s
experiments is not a positive ion but a dust particle which has
* Henry, Proc. Camb. Phil. Soc. 1x. p. 319, 1897.
+ Whiddington, Proc. Camb. Phil. Soc. xv. p. 189, 1909.
+ Lenard, Ann. der Physik, 1. p. 486, 111. p. 298, 1901.
VOL. XV. PT, VI. Bi
484 Mr Hughes, On the Mobilities of the Ions
lost negative electricity in accordance with the ordinary photo-
electric effect at the surfaces of solids or liquids. This view was
confirmed by the experiments of Bloch*, who repeated Lenard’s
experiments in such a way that the air could be rendered free
from dust. With ordinary air he obtained Lenard’s results, with
dust-free air he was unable to detect any conductivity in the air
due to the action of the ultra-violet light.
Professor Sir J. J. Thomson+ has carried out some experiments
in which he found that the ultra-violet light from the glow in the
lime cathode discharge produced a small conductivity in a stream
of air, increasing the current to about six times the natural leak.
In a letter to Nature, Palmer? stated that he found that air
was rendered conducting by ultra-violet light of wave length
shorter than about 2 1850 (Angstrom units). No details are
iven.
: Stark§ has investigated the effect of ultra-violet light on the
conductivity of gases and has obtained positive results with
certain complex organic vapours—anthracene, diphenylmethane,
diphenylamine and @ naphthylamine. Stark concludes from his
experiments on air that Lenard’s results do not indicate a true
ionisation of the air by ultra-violet light. He points out in dis-
cussing researches on the ionisation of air by ultra-violet light,
that, before one can say that a conductivity in air is really due
to ionisation of air molecules, the absence of dust particles and
droplets must be proved and that positive as well as negative ions
must be shown to exist in the air.
I was unable to obtain any definite indication of ionisation of
air due to ultra-violet light which had passed through thin quartz
plates. The sources of light used were the mercury are, the glow
in a lime cathode discharge and the discharge in hydrogen.
There was reason to believe that, if the ionisation of air
depended upon the wave length of the light employed, the
shorter the wave length, the more ionisation one would expect.
Professor Lyman has carried out several important researches
upon ultra-violet light especially in the region of very short wave
lengths. He found that the ultra-violet spectrum of hydrogen
was full of closely packed lines extending down to 1030].
Another research{ of his was carried out to find whether there
was any substance more transparent to ultra-violet light than
quartz. Many substances were tried, but only one—fluorite—
was found to transmit ultra-violet light of shorter wave length
* Bloch, Le Radium, p. 240, 1908.
+ Sir J. J. Thomsen, Proc. Camb. Phil. Soc. x1v. p. 417, 1907.
+ Palmer, Nature, 77, p. 582, 1908.
.§ Stark, Phys. Zeits., Sept. 15, 1909.
|| Lyman, Astrophysical Journal, xxtt. p. 181, 1906.
| Ibid., xxv. p. 45, 1907.
produced in Air by Ultra-Violet Light. 485
than that transmitted by quartz. Thin quartz was found to
transmit down to a wave length 11450 while some specimens
of clear colourless fluorite transmitted down to » 1230.
It therefore seemed more promising to use fluorite instead of
quartz. Several crystals of clear colourless fluorite were obtained
and plates about 2 cms. thick were cut from them. Most of them
in the process of cutting and grinding broke up into bits too
small to be of any use. One plate, however, perfectly free from
flaws was obtained with a clear space of 2 cms. in diameter. This
was the piece used in the following experiments.
The apparatus used is shown in fig. 1. The light is obtained
from the discharge tube LZ. The two electrodes were separated
by a glass tube with a narrow opening facing the fluorite plate.
In this way, great concentration of luminosity was obtained at
the end of the inner tube. The electrodes were connected to the
secondary of a smal! induction coil used as a transformer. The
primary was connected to the electric light mains (alternating)
using as a resistance a few lamps in parallel. With hydrogen
in the tube at a pressure of 2 or 3 mm., a steady source of light
was easily obtained.
The air is drawn in through a wide plug of cotton-wool and
passes up a narrow tube until it reaches the fluorite window.
The end of the tube is within 1 mm. of the fluorite window, which
insures that all the air which passes through the apparatus comes
under the action of the easily absorbed short wave length ultra-
violet light. The air then passes into the ionisation cylinder
through a short glass tube suitably bent to prevent reflection of
the ultra-violet light on the electrodes. For the mobility experi-
ments two electrodes V and F' along the axis were used.
It was found that when the light was produced in JZ, the
stream of air flowing through the ionisation cylinder was highly
conducting and contained both positive and negative ions, the
‘latter predominating. Control experiments were made (1) with
the air in motion but without the light, and (2) with the light
but no motion of the air. Under these conditions there was no
leak in the ionisation cylinder.
To make sure that the positive carriers were not positively
charged dust particles, the air after leaving the ionisation cylinder —
was drawn through a Wilson expansion apparatus where samples
could be tested. With expansions of less than 1:25 no nuclei
were obtained, while above that expansion there was no increase
over the ordinary effect obtained with dust-free air. This showed
that the cotton-wool plug was efficient in removing dust particles.
There seems to be no way of explaining the presence of these
positive ions other than by an actual ionisation of the air by the
ultra-violet light.
32—2
486 Mr Hughes, On the Mobilities of the Ions
In view of Lenard’s results, it appeared advisable to measure
the mobilities of these ions. An absolute determination would
have been more difficult than a comparative one, and for the
purpose of the research hardly as conclusive as a direct comparison
with X-ray ions. The method adopted was a modification of
Zeleny’s* or Rutherford’st.
If ionised air be drawn through the ionisation cylinder (fig. 1)
and the quantities of electricity received in unit time by the
“far” electrode F be plotted against the potentials on the
cylinder, then a curve will be obtained cutting the abscissa at
the smallest potential required to drive all the ions into the
“near” electrode V. The form of this curve will depend upon
the distribution of the ions in the stream of air. One would
expect a fairly uniform distribution on consideration of the way
in which the air streams up against the fluorite window.
Fluerite
» .
Me elechroverfe IN RB elechoserhe
Fig. 1.
In the comparative experiments the air was ionised by X-rays
in as nearly as possible the same place as when ionised by ultra-
violet hght. A beam of X-rays 2 cms. wide was directed at that
portion of the apparatus just under the fluorite window, all other
parts of the apparatus being shielded by thick lead screens. The
X-ray buib was placed at a distance of 25 cms. from the fluorite
window. An idea of the effect of the light may be obtained from
the fact that the positive leak in the apparatus was of the same
order when the ionisation was produced by the light as when
produced by the X-ray bulb working vigorously. (The X-rays
had to pass through the glass tube, the walls of which were 1 mm.
thick.) The negative leak when the ionisation was produced by
the light was about twenty times as large as the positive.
* Zeleny, Phil. Trans. A. 195, p. 193, 1900.
+ Rutherford, Phil, Mag. Vol, 47, p. 109, 1899.
produced in Air by Ultra-Violet Inght. 487
In order to obviate time measurements and to be independent
of any variations in the intensity of the light or of the X-rays,
the quantity of electricity received by the “ near” electrode VV was
measured as well as that received by the “ far” electrode #. The
total quantity received by NV and F was taken as a standard and
the actual value received by F was divided by this. This was the
quantity plotted in the curves.
The velocity of the air was indicated by the pressure drop
across a small plug of cotton-wool at # and was kept at approxi-
mately the same value throughout each series of experiments.
Both electrodes were connected to Wilson tilted electroscopes
and to capacities of about 400 cms. The electroscopes were cali-
brated after each reading by means of a potentiometer.
TABLE J. Jonsation produced by Ultra-Violet Inght.
n=quantity of electricity received by ‘‘ near” electrode.
f= ” ” ” “ far” ”
Fat = quantity of electricity received by ‘‘ far” electrode for a given number of
ions passing into the ionisation cylinder.
|
Potential on ms f RP Potential on
cylinder cylinder
— 8 volts 5) “44
Se)
~y
i=)
+10 volts | °87 “61 | -412
Onaga 1-05. 243 1-200 419) 68 | -35 | -340
ie 1-22, || 83 ||| -214 || 14, 82 | -26 | -241
ee eet 2 lage tem | 296. 220) || 174
Seen eal 10) W218, 9 282 712 | 198
eeu Onee| 07 -OGR 3200 M208) 210: | 093% |
200 M1720) | “O70 | -055 +96 ,, --| 98. | -08. | -029. |
TABLE II. Tontsation renin) by X-rays.
Potential on ” Potential on
cylinder Me I : cylinder i
— 8 volts | -465 Bil el) +10 volts | -463 | :285 | -379
=10 5, regu. | 290 | +12 7, | -500 || -220 |. -306
12 450 BOOP \e:095r 107 | 414. 538 | -180 | -250
Sd, BB08 W069! 11a. I) 216: _,, 538 | 140 | -180
= 16.) 5,1. D4 palleObGs 083 Iele: 565 | -083 | -128
21 Rs ee Wale eee on, 535 | 083 | +134
| +26 ,, | 620 | 058 | -048
Mr Hughes, On the Mobilities of the Tons
The quantities F are plotted against the potentials in figs. 2
488
and 3.
ae ieee!
aa
Lalo ld
Fig. 2.
ABReesaaa
EEE
EEE
RRREEEE ERR EE EERE EE EEEH EEE
{+ X
|
\
Se
AT
va
2
NAY
FEES
ee
N j2* 2a)
YS ESRS
Eto
G3)
FA
N
\
©
\
faa fone bas fos Fra pen] pe)
SEGREEN
Fig. 3.
The curves are in fair agreement, showing at any rate that
produced in Air by Ultra-Violet Light. 489
there is not much difference between the mobilities of the ions
produced by X-rays and those produced by ultra-violet light.
The figures at the end of the tables are not so reliable as those
at the beginning, for example the / corresponding to —18 volts
in Table I is ‘073 and this was calculated from an electroscope
reading of ‘8 of a division, which from its small size is liable to
considerable error.
Absolute agreement between the two sets of curves could only
be expected if the ions were distributed in the stream of air in
precisely the same way. It was thought, however, that considera-
tions of this sort could not wholly explain the differences between
the results given above and that a better agreement was possible.
As nearly ali the negative ions in the experiment may be put
down to surface ionisation, it was not necessary to investigate
their mobilities, for Rutherford* has shown that surface ions are
identical with negative. ions produced by X-rays, etc. The results
for the positive and the negative ions produced by ultra-violet
light and the positive ions only produced by X-rays are given in
Tables III and IV.
During the short time occupied in taking a reading, the
velocity of the air did not alter appreciably, but it was difficult
to adjust the velocity each time to exactly the same value. A
small correction was therefore made in the figures of Tables III
and IV. The pressure drop across the cotton-wool plug # was
about 150 cms., and it was assumed that the variations in the
velocity of the air were proportional to the small deviations from
this value and that the quantity of electricity / was increased in
the same proportion. ‘Therefore, to obtain the value of Ff for a
standard velocity corresponding to a pressure drop of 150 cms.
the value was diminished in proportion to the eacess of the
pressure over 150 cms. and conversely. This correction, which
was never more than about 5°/, or 6°/, brought the results into
better agreement.
TaBLe III. Tonisation by Ultra-Violet Light.
Potential F Potential F
— 6 volts 522 + 8 volts ‘415
eames oe 312 +10 ,, 367
—10 ,, I) aA se Ye 256
—-12 ,, 156 | +14 _,, IL Ff
—14 ,, ‘117 ateiGat 3 “151
—16 ,, 059 +18 ,, PILL
-18 ,, 038 +20. ,, ‘073
+26 ,, ‘041
* Rutherford, Proc. Camb. Phil. Soc. 1x. p. 401, 1898.
4.90 Mr Hughes, On the Mobilities of the Ions
TABLE IV. Jonisation by X-rays.
3 - F (ultra-violet),
Potential i F from Table III f R ee
+10 volts 348 367 +°019
12 <5 248 256 + 008
a 210 “217 + ‘007
SDE TG Bias ‘158 “151 — 007
eS) ee 132 “102 — ‘020
os 078 073 ~-005
+26 ,, 082 041 —:041
on
au s#oeesh god seuazeseeaeccet :
If a |
3 a se aise a
| ae - |
a i ia
2 == a
rH i
{_| |
te
of .
Pry aie | |
{|
4 HH
8 10 EY aT 1%, «2002~«*
Fig. 4.
third column in Table IV is copied from Table III for comparison
with the second column and the outstanding differences are given
in the last column. From these results, it may be concluded that
the mobilities of the positive ions produced by ultra-violet light
and by X-rays are identical.
a
produced in Atr by Ultra-Violet Light. 491
The piece of fluorite used in the experiment was the only
piece which would transmit ultra-violet light capable of producing
positive ions in any quantity. Many other pieces cut from different
erystals seemed opaque to the radiation producing the positive
ions, but in every case the negative (surface) ions were obtained
though in less quantity than before. In this connection Lyman’s
work shows that the limit of the spectrum transmitted by fluorite
varies considerably in different specimens. The shortest wave
length transmitted was 11230. These results suggest that the
ionisation of air by ultra-violet light sets in at some wave length
between 21230 and 271450 and increases very rapidly with
decreasing wave length.
I have great pleasure in thanking Professor Sir J. J. Thomson
for suggesting the investigation to me and for his interest in the
course of the work.
492 Mr Beatty, A Dissymmetry in Emission of Cathode Particles
On a Dissymmetry in the Emission of the Cathode Particles
which are produced by Homogeneous Réntgen Radiations. By
R. T. Bearry, M.A., B.E., Emmanuel College. (Communicated
by Professor Sir J. J. Thomson.)
[Read 9 May 1910.]
When Roéntgen radiations fall upon certain metals, homo-
geneous secondary radiations are produced. If one places a thin
metallic sheet in the path of such a homogeneous radiation,
cathode particles will emerge from both surfaces of the sheet.
The object of the present research is to find out what ratio exists
between the quantities of cathode energy leaving the front and
back surfaces.
Eo 200 volts.
to electroycope
me eee a
Fig. 1.
A shallow cylindrical brass ionisation chamber (fig. 1) received
the radiations through a thin parchment window PP in its lower
side. RRisaring cathode. Two concentric circles were cut out
of a sheet of cardboard and an annulus was thus formed which
had an external diameter equal to that of the ring electrode, while
its internal diameter was about 2 cms. less. A silver leaf (equiva-
lent in weight to 2 mm. of air) was laid upon two sheets of thin
paper (each sheet being equivalent to 1 cm. of air) and the whole
was tightly gripped between two cardboard rings made as de-
scribed, and gummed at the edges.
A second specimen was now made of the exact dimensions of
the first, but in this case the silver leaf was placed between the
two sheets of paper, the latter absorbing all the cathode particles
from the silver.
These rings were placed in turn on RR, and the ionisation
measured when a given radiation entered through the window
PP. A second electroscope was used to standardise the radiation.
Now in one cardboard ring the arrangement was paper—
silver leaf-paper. Let us call this ring O since no cathode par-
ticles can escape through the paper. The second ring was made
up of silver leaf-paper-paper. We may call this C since cathode
particles do escape from one side of the leaf.
which wre produced by Homogeneous Réntgen Radiations. 493
Now if we take a reading with O in position, and another
with O replaced by C, the silver leaf being uppermost, the differ-
ence will represent the ionisation due to cathode particles on the
emergent side of C. The direct ionisation due to Réntgen radiation:
will be the same in both cases, since 0 and C absorb the radiation
equally,
If now we reverse C, we can in the same way find the ionisation
due to the cathode particles on the incident side of the silver leaf.
We must make a correction in the emergent case since the radia-
tion passing through the leaf has been absorbed to some extent
by the paper and the leaf itself.
The cathode particles due to soft radiations (Fe, Cu) emerge
only from a small fraction of the thickness of the leaf. Hence we
may assume that in the emergent case, the radiation has suffered
absorption by the whole thickness of the leaf.
This absorption was found to be 14°8°/, for the Fe radiation.
Hence the emergence values were multiplied by to bring
100
85°2
them up to the value which they would have had if the Fe
radiation had suffered no absorption.
Energy of emergent cathode
1) incident pra 3
Silver leaf.
TasBLeE I, Ratio=
Radiator Uncorrected ratio Mean Corrected ratio
846
Fe 860 ‘869 1:02
‘901
‘995
Cu uh 930 1:01
‘931
: 1:09 ;
Se {ros} 1-085 1-10
1:30
Ag {1 98} 1-29 1-29
{ 1°30 i ,
Sn {1-306} 1-303 1-303
1°44
Al {1 is 1-435 1-435
Similar corrections were made for the Cu and Se radiations.
The corrections for the harder radiations were negligible. The
change in the secondary radiation from the leaf when O and C were
494 Mr Beatty, On a Dissymmetry in the Emission, ete.
interchanged was also negligible. The radiation from Al was
excited by very penetrating rays from the bulb, and was passed
through Al sheets to cut out the softer portions.
On repeating the experiments with a Cu leaf replacing that
of Ag, similar results were obtained (Table I1).
TABLE II. Comparison of ratios for Ag and Cu.
Radiator Ratio, Ag leaf | Ratio, Cu leaf
Fe 1:02 —
Cu 1:01 —
Se 1:10 1:08
Ag 1:29 —
Sn 1:303 1:319
Al 1:435 1:42
In the case of the Cu leaf the cathode energy excited by the
Fe and Cu radiations was too small to measure.
It will be seen that:
1°. A dissymmetry exists in the amount of energy due to
cathode particles emerging from opposite sides of a metal sheet.
This dissymmetry increases as the radiation becomes more pene-
trating.
2°. For a given radiation the dissymmetry is the same for
Ag and Cu leaves.
Bragg and Glasson* have shown that a similar dissymmetry
exists In the case of secondary Réntgen radiations. They state,
however, that when the secondary radiator is Fe or Cu, both of
which give out a quantity of homogeneous soft secondary radiation,
the dissymmetry is greatly reduced.
In the present research Cu and Ag leaves were used because in
the former case the homogeneous radiation is much more easily
excited. The dissymmetry in the cathode distribution appears to
be independent of the presence or absence of excited homogeneous
radiation.
I beg to thank Professor Sir J. J. Thomson for his interest in
this investigation.
* “On a Want of Symmetry shown by Secondary X-Rays,” Philosophical
Magazine, June, 1909, p. 855.
Mr Compton, On Right- and Left-Handedness in Barley. 495
On Right- and Left-Handedness in Barley. By R. H.
Compton, B.A., Frank Smart Student of Gonville and Caius
College.
[Recewwed 6 June 1 910.]
A seed of barley produces on germination a tubular sheath
through which the first green leaf emerges. This first leaf is so
folded that one margin overlaps the other, at first throughout nearly
its entire length; later on, after more leaves have been produced,
only the lower sheathing portion retains the original fold. In
some cases the right-hand margin overlaps, in others the left-hand.
A convention is necessary in the use of these terms: the one used
here is illustrated by figure 1. ‘The observer is supposed to be
AIRS Tete.
LEAF
- SHEATH ---
Fig. 1.
Diagram of the two ‘‘ stereo-isomeric”’ forms of Barley seedling.
standing in the axis of the plant, facing outwards through the
open side of the leaf, and folding one hand over the other to
496 Mr Compton, On Raght- and Left-Handedness in Barley.
imitate the leaf-margins. The condition with the right margin
overlapping is called right-handed ; that in which the left margin
overlaps is called left-handed*.
Leaves subsequent to the first are also twisted: the normal
arrangement appears to be that R.H. and L.H. leaves alternate all
the way up the stem; Le. if the first leaf be L.u. the second will
be B.H., the third L.H., and so on. But this rule is subject to
frequent exceptions in which the arrangement may be irregular
and two or more successive leaves may have the same twist.
The frequency of these exceptions, as well as the difficulty of
accounting for them, suggest that the characters of right- and
left-handedness are largely under the influence of slight “ac-
cidental” causes, of whose nature we are ignorantt.
The fertile axis bears a series of alternate notches in which
are inserted the flowers, three to each notch. In six-rowed
barley all three flowers set seed; in two-rowed barley only the
middle flower of each group of three. I shall speak of the “odd”
and “even” notches in the spike; the odd being numbers 1, 3, 5,...,
and the evens being numbers 2, 4, 6,..., reckoning from the base
upwards. The first few flowers are usually sterile.
On flowering the anthers may be extruded, and pollen
scattered; but the flowers do not open, and the stigmas never
come outside the glumes. Consequently, self-pollination is
regularly effected. Prof. Biffen tells me that he has never
detected any signs of crossing. It is possible, though not without
much difficulty, to perform emasculation and cross-pollination of
the flowers: and I have made a few such crosses. The results
were meagre, however, and as, for reasons to be explained below,
they throw no light on the problem, no further mention will be
made of them.
I have worked almost entirely with two-rowed varieties of
barley, because some of the manipulation is thereby simplified.
The following points will be considered :
* There is never any real doubt whether the seedling is R.H. or L.H. Occasion-
ally plants are found in which both margins of the leaf appear to be inrolled: but
inspection shows that at the base of the leaf the normal overlapping occurs. Among
4000 seedlings 15 such were found.
In one case a single seed produced on germination two shoots of equal size: of
these one had the first leaf r-H. the other 1.x.
The auricles at the junction of leaf-blade with sheath follow the twist of the
leaf: that auricle being lower which is on the overlapping margin.
+ See Stratton and Compton, ‘‘On Accident in Heredity,” in the present number
of these Proceedings, p. 507.
This overlapping of leaf-margins is entirely different from the rolling of the
leaf blades of grasses which is used as a taxonomic character in agriculture. See
for example Percival, Agricultural Botany, p. 511, where barley, wheat and rye are
said to have the ‘‘leaf-blades rolled to the right,” while in oats the leaf-blade is
‘‘ generally rolled to the left.” See also Hackel, in Engler and Prantl’s Nat. Pjifam.
‘‘ Gramineae,” p. 4.
Mr Compton, On Right- and Left-Handedness in Barley. 497
(1) The ratios of lefts to rights found in the first leaves of
large groups of seedlings of different varieties.
(2) The ratios obtained from individual spikes of seed.
(3) The question whether the twist of the last leaf below
the spike has any effect on the twist of the seedlings produced
from the spike.
(4) The question as to the effect of the position of a seed
in the spike on the twist of the seedling produced from it.
(5) The question whether the twist of the first leaf is
inherited.
I. The seeds of certain varieties of barley were sown in large
numbers in the ground or on wet canvas or blotting-paper, and
the seedlings were counted with a view to determining the ratio
of rights to lefts among the first leaves. The following are the
tabulated results:
TABLE I.
Variety of Barley LH. R.H. eae ieee
Plumage Corn (pure line). | 2408 1604 1501 60:02
Archer: Danish (pure line) 765 508 1-506 60-09
LIEGE EES AR ae Se RR 819 586 1-389 58-29
Chevalier: Kinver ......... 730 546 1:337 57°21
Chevalier: Prize Prolific... 405 299 1-354 57°53
Goldthorpe (pure line)...... 608 463 1:313 56-77
Goldthorpe: Guinness...... 740 587 1-261 55-77
New Binder (pure line) ... 762 571 1:335 57°16
Pocalenenas 1237 5164 1-401 58°36
From the above table it is clear that there is a considerable
excess of left-handed over right-handed first leaves in large
groups of seedlings. Adding all the plants examined together,
we find that out of a total of 12,401 seedlings 58°36°/, had the
first leaf twisted in the left-handed fashion. The number of
seedlings examined, and the constant occurrence of the excess of
lefts in all the varieties studied seem entirely to preclude the
assumption that this preponderance of lefts is fortuitous.
The ratios obtained in different kinds of barley vary to some
extent. It appears probable that the difference between Plumage
Corn and Guinness’ Goldthorpe, for example, is significant: it
seems to be outside the limits of probable error, when we con-
sider the number of plants counted—4012 in Plumage Corn,
498 Mr Compton, On Right- and Left-Handedness in Barley.
1327 in Guinness’ Goldthorpe. With regard to the intermediate
ratios it is unwise to dogmatise: but it appears likely that
differences should exist between different races of barley in this
respect.
It is difficult to know how to interpret these results. It is
interesting, however, to compare the ratios obtained for barley
with those recorded in certain other cases of right- and left-
handedness.
In a paper on the inheritance in man of the mode of clasping
the hands, Lutz* states that of the total population investigated
61°/, of the males and 58°/, of the females habitually cross the
right thumb over the left. Here the same percentage occurs as
in barley.
In Anableps anableps, a Cyprinodont fish, the anal fin is turned
either to the right or to the left in different individuals. Garmant
found that about 2 of the males are dextral, 2 sinistral: in the
females the ratios are reversed. Here again each sex shows a
percentage of 60 as between rights and lefts.
Though the repeated occurrence of this percentage is remark-
able, there are cases in which practical equality of rights and lefts
is found. For instance, in the males of the Fiddler Crabs,
Gelasimus pugilator and G. pugnax, where the chelae are un-
equally developed, Yerkes? states that out of nearly 3000
specimens he found almost equal numbers of rights and lefts.
In species of cotton, right- and left-handed plants may be dis-
tinguished according as the accessory bud is on the right- or left-
hand side of the median axillary bud. Leake§ found that nearly
equal numbers of both sorts of plants are produced, and considers
that right- and left-handedness do not follow the ordinary laws of
inheritance.
In Teleost fishes the optic nerves cross one another at the
optic chiasma. Parker|| examined a hundred specimens of each
of ten species of teleosts, and found 514 with the nerve from the
right eye dorsal, 486 with it ventral. Individual species all
approximated fairly closely to the ratio of equality. Larrabee {]
investigated the matter further, and found that a random collec-
* Amer. Naturalist, xu11. 1908, p. 195. My own experience, however, seems to
indicate a preponderance of persons who cross the left thumb over the right.
+ Amer. Naturalist, xxtx. 1895, p. 1012.
+ Proc. Amer. Acad. of Arts and Sci. xxxvi. 1901, no. 24. Yerkes considers
that the occurrence in equal numbers of right- and left-handed Fiddler Crabs shows
that these characters are not hereditary, but are due to chance (p. 440). This is
clearly a mistake, for the ratio equality in a population may readily occur in cases
of Mendelian inheritance: but in any case Yerkes’ data are not competent to settle
the question of the application of heredity to this instance of right- and left-
handedness.
§ Journ. and Proc. Asiatic Soc. Bengal, v. 1909, p. 23.
|| Bull. Mus. Comp. Zool. Harvard, xu. 1903, no. 5, p. 219.
{| Proc. Amer. Acad. of Arts and Sci. xutt. 1906, no. 12.
Mr Compton, On Right- and Left-Handedness in Barley. 499
tion of 650 brook trout included 365 with the right-eye nerve
dorsal, 285 with it ventral: this being 56:1°/, of right-handed
individuals. Among 4615 trout, including the above numbers
and also the offspring of several selected matings, Larrabee found
that 56°/, had the nerve of the right eye dorsal. Since he showed
that the dimorphism is not hereditary, it seems probable that this
percentage is significant.
The case of Gryllus, investigated by Lutz*, is interesting as
an instance of a species typically of one only of the two “stereo-
isomeric ” forms, in which accident causes a certain proportion of
individuals to assume the reverse form.
The extraordinary results obtained by Mayerf, in some species
of the land-snails, Partula from Tahiti, may be mentioned here, as
showing that the proportion of rights and lefts may vary with the
geographical race.
In many asymmetric Mollusca the occurrence of the twist the
reverse of normal is sporadic, the abnormal specimens never reaching
a high proportion. In the Achatinellidae Gulick§ states that
some species are normally dextral, others normally sinistral, while
others again are both dextral and sinistral: but the proportions
of rights and lefts in the last cases are not, so far as I know, on
record.
In the other cases which I have been able to collect from the
very scattered literature the number of rights and’ lefts were too
small to fix the ratio with exactness.
* # # *
The constancy of the ratio in successive generations of barley
is attested by the following table, giving two years’ counts in the
same family of Kinver Chevalier.
TABLE II.
Twist of first leaf
Year Ratio | Percentage
L.H./R.H. L.H.
L.H. R.H.
IOC a ar ane a ee ee 730 546 1:337 57:21
ROMO Ves caddie 379 259 1:463 59-40
Expectation for 1910 on
TPO ple BONA Lies 3 tonsa: 364 274
* Canadian Entomologist, xxxviu. p. 207.
+ Mem. Mus. Comp. Zool. Harvard, xxv1. 1902, no. 2.
+ A useful summary of such cases is given by Sykes, in Proc. Malacol. Soc. vi.
1905, p. 253.
§ ‘‘HKvolution, Racial and Habitudinal,” Carnegie Institute Publications, xxv.
1905
VOL. XV. PT. VI. 33
500 Mr Compton, On Right- and Left-Handedness in Barley.
The discrepancy between the two generations is only such as
would be removed by a turn-over of fifteen lefts to rights,
assuming the 1909 ratio to be absolutely accurate.
In this connection it should be remarked that stability of
population with regard to certain characters occurs, in the
absence of selection, as a result of the Mendelian inheritance of
those characters*. Hence the occurrence of a stable ratio in this
case is not in itself incompatible with the inheritance of the
characters concerned in a Mendelian fashion: though of course it
does not necessarily tend towards such a view, other alternatives
being possible.
II. The ratios for whole populations having been obtained,
the question arises as to the ratios given by individual spikes of
fruit on germination. In order to determine this a number of
ears of “Plumage Corn” barley were laid whole on wet blotting-
paper, and on germination the seedlings of each spike were counted
for rights and lefts among the first leaves. Each seedling was
classified according to:
(i) The twist of the last foliage leaf below the spike,
whether right or left.
(ii) The row of seeds in the ear from which the seedling
arose, whether odd or even.
The percentages of left-handed seedlings for each individual
spike, in which a reasonable number of seeds (more than ten) ger-
minated, were calculated; and curves were drawn expressing the
relation of these percentages to the frequency of each percentage.
The curves were obtained by plotting, at intervals corresponding
to every 5°/,, the number of percentages included in a range of
5°/, on either side. Thus the number plotted for 60°/, is that of
the percentages between 55°/, and 65°/,: the number plotted at
65°/, is that of the percentages between 60°/, and 70°/,: and so
on. The curve for spikes above L.H. last leaves is drawn as a
continuous line (the lower in the diagram); that for those above
R.H. last leaves as a dotted line: there were 86 spikes of each
class. The taller continuous curve is given by all the 172 spikes
taken together.
The curves for the spikes above L.H. and R.H. last leaves
respectively differ somewhat in shape. The former is steeper and
narrower, and indicates less range of variability than the latter.
The curve for R.H. top leaves shows two slight maxima, with a
minimum where the other curve reaches its maximum. It would
be unwise to lay stress on these differences, however, as they are
not very pronounced. The total curve is of a form very usual
in studies of variability. It is practically symmetrical about its
* Hardy, Science, N.S., xxv. 1908, p. 49.
Mr Compton, On Right- and Left-Handedness in Barley. 501
mode, which is at 60°/,. This percentage is the same as the
average given by the whole population of seedlings. There is no
sign (except possibly in the curve for R.u. top leaves) of any
segregation, or of a separation into “pure lines.” It would be
interesting to study other varieties of barley, not of pure lines,
SSeS
| See eae
Ea ne ie
Ae
is
i - = ae
A
eee
ame jo cEam
eee
fee SINT
PRR
eee Pro e
Pca
me NN
V SS
a) SE es
6 6 /. SOS TO VG TO
30
0
PERCENTAGES
or which give different ratios of rights and lefts in the total
population, and to determine in what way the curves of percentages
differ from those given by the pure line “ Plumage Corn.”
* * # * *
The results of this portion of the investigation are summarised
below in tabular form, which displays certain facts not exhibited
by the curves. (Table III.)
III. Table III shows conclusively that the twist of the last
foliage leaf, immediately below a spike, has no effect whatever on
the ratio of left- to right-handed seedlings borne by that spike.
The correspondence between the two classes of spikes is indeed
extraordinarily close, and tends to confirm the accuracy of the
ratio 15 as expressing the proportion of lefts to rights in
“Plumage Corn.”
339
502 Mr Compton, On Right- and Left-Handedness in Barley.
991, 671 6€8 8GeL
“|, 60-09 ‘|. 86-69 “1, 94-09
L0G: I FO9T 80FG 6GP-1 18Z VEIL 8rG-1 668 FLL
604-1 182 VLIL GLY-1 GLE Egg 669-1 90V 1e9
667-1 668 FECL Té7-1 907 18g 99¢-1 LIV 699
‘WaT bce a “Hu HT oer ono Ha / HT onaeret SORT
oryey oryery OTyey
[e}0], spedg UaAT sp92g ppo
ooo
TIL Fav,
| suea9 pue sppo
yyoq 09 sordde ¢.1
onel Jt “WoTyezoodxn
Paigree ‘TROT,
(sextds GoT)
ra we ae
(soxtds 19)
ae ay °F ERED)
ayIds oy} MOTE
JRO] OBVITOF 4SV] JO STAT,
Mr Compton, On Right- and Left-Handedness in Barley. 503
IV. The question as to a possible regularity in the arrange-
ment on the parent plant of seeds bearing definite characters is
of great interest. Prof. Bateson considers that there is a strong
@ priory presumption that some regularity exists: but as he and
Miss Killby were unable to discover any such regularity in Peas,
he is “disposed to think that the process of odgenesis in which
the dominant or recessive character of the egg-cell is determined
must be liable to disturbance by accidents*.”
In the present case it appeared probable that some such
arrangement might be discovered ; though, as will be shown later,
there is here no evidence of heredity. But the character under
consideration is one of symmetry, and is determined early in
embryogeny ; and it seemed not unreasonable to expect that the
symmetry of the parent spike might have some clear influence
over the symmetry of the embryos borne upon it.
The attempt to discover such an order of arrangement of the
right- and left-handed offspring on the parent ear gave, however,
inconclusive results. Table III shows the aggregate numbers for
the odd and even rows of seeds on the spike. It will be seen
A »H.
that the ratio Z
R.
in seeds from odd rows is slightly higher than
in those from even rows. The total difference is 153°/,. This
discrepancy might be considered insignificant, were it not that
the accuracy of the counts, as judged by the agreement between
the two classes of spikes, appears to be very high. The fact that
both classes of spikes gave a difference between odds and evens
in the same direction is also slightly in favour of regarding this
difference as significant.
Clearly, however, the evidence is inconclusive ; and it would
be rash to try to found upon it any theory of the influence of the
position of the seed on the parent on the character of the seedling
developing therefrom.
No more significant result was obtained by a study of indi-
vidual spikes. Many single ears of “Plumage Corn,’ “ Kinver
Chevalier” and “Goldthorpe” were examined carefully with a
view to discovering any regularity which might exist in the
arrangement of the seedlings borne upon them. No such regu-
larity was discernible, however.
In a paper by Mackloskie+ the following statement is made:
“The grains arising on adjoining rows in the ear of corn [maize]
are of different castes, and produce ‘antidromic’ plants (that is,
growing up in opposing curves), and that the same property
belongs to all the Gramineae.” So remarkable is this assertion in
the light of the above results for barley, that I repeated Mack-
loskie’s experiment on maize; but completely failed to confirm
* Reports to the Evolution Committee of the Royal Society, 11. 1905, p. 69.
+ ‘ Antidromy in Plants,” Amer. Naturalist, xx1x. 1895, p. 973.
504 Mr Compton, On Right- and Left-Handedness in Barley.
his statement. Here as in barley there appeared to be no
regularity in the arrangement of the two sorts of seeds on the ear.
V. Inheritance. In the case of the mode of clasping the
hands, Lutz* found that the marriages of R.H. by RB.H. gave a
considerable preponderance of R.H. among the offspring; those of
L.H. by L.H. gave an excess of LH. children; while those of R.H.
by LH. gave intermediate ratios. Thus the mode of clasping the
hands appears to be inherited in some wayf.
In the case of the optic chiasma in Teleosts, Larrabee | showed
that inheritance of the dimorphic condition cannot be detected
either by Mendelian or Galtonian methods.
With respect to this subject of the inheritance of characters of
symmetry it is almost impossible to form an a@ priori opinion;
and it 1s an open question which is the more remarkable fact—the
inheritance of the mode of clasping the hands or the non-in-
heritance of the dimorphism of the optic chiasma. Much more
investigation is necessary to determine the essential distinction
that produces the different behaviour of the two similar sets of
characters.
The case of barley agrees with that of the optic chiasma in
that no inheritance is discernible. This appears to be the con-
clusion that must be drawn from the following statistics.
The seeds produced in 1909 by 36 plants, the twist of whose
first leaf was known, were sown in 1910, each ear of grain being
treated separately. The following are the tabulated numbers of
right- and left-handed first leaves among the seedlings; all the
seedlings produced being included, whether they were borne on
the main spike or on “ tillers.”
TaBLeE IV. (Kinver Chevalier.)
L.H. first leaf |R.H. first leaf ca
Total seedlings from plants ;
<Hiih an, feat len IOUS | Ie af Lee.
(Expectation on ratio 1:463 137 94)
Total seedlings from plants : ae
Wain tee imag len’, 1908 seo ee ao
(Expectation on ratio 1-463 242 165)
Grand total......... 379 259 1-463
* Amer. Naturalist, xu1t. 1908, p. 195.
+ See Stratton and Compton, ‘‘On Accident in Heredity,” in the present number
_ of these Proceedings, p. 507.
t+ Proc. Amer. Acad. of Arts and Sci. xu. 1906, no. 12.
*
Mr Compton, On Right- and Left-Handedness in Barley. 505
It is true that this table does not reach the same degree of
precision as that attamed in the previous discussion, the numbers
recorded being smaller. But there appears to be no reason to
doubt its substantial accuracy. The ratios given by the offspring
of right- and left-handed seedlings respectively are so nearly the
same that it seems impossible to detect any hereditary nexus
between successive generations. The fact that the proportion of
R.H. seedlings produced from (self-fertilised) left-handed plants is
slightly greater than that produced from (self-fertilised) right-
handed plants seems to emphasise this negative answer to the
problem.
* * * % *
The absence of influence of the first leaf on the ratio given
by the spike, taken with the similar absence of influence of the
last leaf (p. 501), leads to the conclusion that these vegetative
characters of the parent plant do not govern the ratio of rights to
lefts among the offspring.
Conclusion.
We are confronted with the fact that a random collection of a
reasonable number of barley seeds always produces, so far as
known, an excess of seedlings with the first leaf twisted in what
may be called the left-handed direction. The ratio of lefts to
rights in the case of “Plumage Corn” (the variety most accu-
rately studied) approximates very closely to 1:5; in other varieties
similar or smaller ratios are found.
Statistics show that :
(i) The twist of the last leaf below a spike has no influence
whatever on the ratio of right- to left-handed seedlings produced
from that spike.
(ii) The same ratio subsists among the seedlings whether
produced from the odd or even rows of seed on the parent ear:
and no orderly arrangement of seedlings with respect to the twist
of the first leaf could be detected on the ear.
iii) The ratio among the seedlings is not governed by the
twist of the first leaf of the parent plant: ie. the characters of
right- and left-handedness in barley appear not to be hereditary.
Thus the reason for the production of the excess of left-
handed seedlings remains an unsolved problem. It seems clear
that the cause of this constant excess must be one of some
subtlety, such as is usually classed as “accidental.” It is possible,
of course, to assume that barley is genetically left-handed, and
that a constant proportion (in “ Plumage Corn” 40°/,) of “acci-
dental” reversals occur in every population and in each generation.
This explanation would cover the observed facts: but it would
506 Mr Compton, On Right- and Left-Handedness in Barley.
hardly change the real problem, which is the nature of the factor
determining the assumed accidental reversal.
The twist of the first leaf is determined early in embryogeny ;
so that the period during which the accidental influence must act
is quite limited. Thus it seems possible to conduct experiments
on the maturing ears by manipulating the orientation or the
environment: and this I hope to do in the future. It has been
thought worth while to publish the above results, as marking a
definite step taken in analysing the problem under consideration.
Finally, I wish to express my gratitude to Prof. Bateson, who
suggested the investigation ; to Prof. Bitfen, who has most kindly
supplied me with seed and with information; to my parents and
sister, and to several friends at the Botanical Laboratory, who
have greatly assisted me in the labour of counting the seedlings ;
and to Mr F. J. M. Stratton who helped me with the curves.
Messrs Stratton and Compton, On Accident in Heredity, etc. 507
On Accident in Heredity, with special reference to Raight- and
Left-Handedness. By F. J. M. Stratton, M.A., Gonville and
Caius College, and R. H. Compton, B.A., Gonville and Caius
College.
[Received 6 June 1910.}
The characters which an organism exhibits are the product of
the action of the environment upon the potentialities inherited
from its ancestry. The external conditions may have the effect of
preventing the manifestation of an inherited character. For
instance, a plant grown entirely in the dark is unable to develop
chlorophyll in its plastids. The chlorotic condition induced in
this way, though much the same in outward appearance, is of a
different nature to that which occurs in a quarter of the seedlings —
produced by the self-fertilisation of the variegated “aurea”
variety of Antirrhinum, where the “ presence of chlorophyll” is a
Mendelian factor segregating against “absence of chlorophyll*.”
It is thus readily possible for two organisms to exhibit the
same peculiarity, in the one case as a result of characters inherited
from the parents, in the other case owing to the direct action of
external conditions.
The case of right- and left-handedness seems to afford a
striking example of the possibility of the inversion of inherited
characters owing to unknown causes, which we may provisionally
eall “accidents.” The difficulty in analysing the facts in human
right- and left-handedness is extreme: especially is this the case
in discussing the main functional asymmetry in man, since it is
almost impossible to allow for the varying influences of education.
But this is not the only source of difficulty. Right- and left-
handedness are characters which, though sharply distinct, are yet
often of an extremely unsubstantial nature as regards heredity.
For example, the mode of clasping the hands with fingers inter-
locking, varies in different persons: and though the distinction
between a person who crosses the right thumb over the left and
one who clasps hands in the reverse way is perfectly sharp, yet
the real difference between the two persons is obviously trifling.
Such an asymmetry we may well expect to be highly susceptible
to accidental influences; and it appears probable that a change of
character may readily occur. So that a person naturally right-
handed in respect of clasping the hands may through accident
become apparently left-handed, and vice versa.
Two examples may be mentioned in order to emphasize this
probability of inversion of character in cases of right- and left-
handedness,
The leaves of many Gramineae (e.g. barley, maize) are folded
* Baur, Ber. d. d. Bot. Gesellsch. xxv. 1907, p. 442.
508 Messrs Stratton and Compton, On Accident in Heredity,
so that one margin overlaps the other*. Accordingly there are
possible two kinds of folding, which may be distinguished as
right- and left-handed. Considering the series of leaves on a
stem, the rule is that the twist of successive leaves is alternately
right- and left-handed. If the first leaf is RH. the second will
normally be L.H., the third R.H., and so on. But a disturbance of
this regular sequence often occurs, with the result that two or
more leaves of the same twist arise in succession. This inversion
of the normal twist of a leaf or Jeaves appears to be the result
of some accidental condition, so slight as to escape notice, but
nevertheless sufficient to effect the change from R.H. to L.H., or
vice versa.
The second case was investigated by Lutz}, in an American
species of Gryllus, in which one tegmen overlaps the other.
Among the $s Lutz found a total of 742 with the right, 370 with
the left, tegmen uppermost. In the 's, however, he found 685
rights to only 13 lefts. The reason for this distinction between
¢ and ¥¢ appears to be the smaller amount by which the tegmina
overlap in the ¢ than in the /: hence a change in the position
of the tegmina is more readily effected in the ? than in the ¢.
Reversal can be produced by manipulation in the 2, but in the
of discomfort is caused to the insect and the tegmina are soon
moved back to their original position{. Here we have a clear
example of the effect of accident in producing left-handed
members in what appears to be a normally right-handed race of
organisms. The difference between the § and ? Gryllus in
susceptibility to accident is very instructive.
To return now to the mode of clasping the hands in man.
Lutz§ analysed statistics which had been collected by Prof. J. A.
Thomson with a view to discovering whether this character is
inherited. The following are his results, condensed from his
table:
Parents No. of Families CES D 2 Percentage of 8.4.
R.H. L.H.
¢Rx OR. 7D 166 63 72°5
¢Rx OL 49 61 49 55-5
$ux QR 53 86 64 57:3
Oulex QL 36 46 63 42:2
* See Compton, ‘‘On Right- and Left-Handedness in Barley,” in the present
number of these Proceedings, p. 495.
+ Canadian Entomologist, xxxvit. p. 207.
{ The ¢s, however, can be made to reverse tegmina while still soft after the
moult; and this is perhaps the origin of the few left-handed ¢s.
§ American Naturalist, xu11. 1908, p. 195.
a
with special reference to Right- and Left-Handedness. 509
Clearly the mode of clasping the hands is inherited in some
way: it remains to find a reason why neither the right- nor the
left-handed character breeds true.
It seems probable to us that the explanation is to be found
in the “accidental” conversion of genetically right-handed in-
dividuals into the left-handed condition, and vice versa. If this
were the case, among a number of apparent rights there would be
a certain proportion of genetic lefts; so that their failure to breed
true to the right-handed character would in part be due to the
admixture of genetically left-handed persons with the apparently
right-handed. Further, the same possibility of accidental reversal
would apply to the offspring, so that, even if genetically pure right-
handed individuals interbred, a certain proportion of the children
would appear to be left-handed. All this would of course apply
equally to the mating of the left-handed, real and apparent.
* * # * *
Making certain assumptions as to the way in which accidental
causes affect the appearance of a character it is easy to see how
the inheritance of the character will be modified. The simplest
assumptions seem to be that a constant proportion of individuals
are affected, and that the change takes place indifferently in either
direction. Let the population consist of true homozygous domi-
nants (DD), heterozygotes (DR), and homozygous.recessives (RR)
in the proportion
DID 9 IDits tly) OVOP 2 Tee
Then for stability through successive generations the equation
must be satisfied *,
Now let @ be the fraction of accidental changes taking place
either way, so that the apparent distribution of dominants to
recessives will be given by
(p+ 2q)(1—@)+7r0@ _ number of dominants (D) (2)
r(1—6)+(p+2q)@ number of recessives(R) ~"”
The value of this ratio is of course known from a count of the
population.
We assume that the mating is random, and examine first the
offspring resulting from the mating of apparent dominants. Since
the proportion of true dominants to factitious ones in the apparent
dominants is
(p+29) (1-6) : 76,
the true matings will be in the proportion
dominant x dominant : dominant x recessive : recessive x recessive
= {(p+2q)(1—6)}?: 2r (p+ 2q)(1—0) 0: 7°.
* G. H. Hardy, Science, N.S., xxvii. 1908, p. 49.
510 Messrs Stratton and Compton, On Accident in Heredity,
Now the offspring of a cross true D x D will be
dominant : recessive = p? + 4pq + 3q?: q?,
i p+ 4pq + 3¢
(p+ 29)
The offspring of a cross true D x Rf will be
dominant : recessive=p+q : q,
of the offspring will be D’s.
jong
Ds 29
The offspring of true A x R will be all R's.
The proportion of D’s to f’s in the offspring of the apparent
D x D crosses will be
(p? + 4pg + 39°) (1 — 6) + 2r (p +g) (1 — 8) 8: PA — ey
+ 2rq(1-—0)0+ 7°,
of the offspring will be D’s.
or say B.C &
These offspring will have a constant proportion transformed,
and we shall have an apparent distribution of the offspring in
the ratio
AGUS Gian Ve 19) 3)
V¥26)4X0 Re hae (8).
In a similar way we can obtain the ratio of the true D’s to
true Ff’s resultmg from the apparent Dx R crosses. They are
(p? + 4pq + 3q?) (1-0) 0 +7r(ptq) — 20 + 26): @—8)@
+rq(1— 26 + 26) +7? (1 — 8) 8,
or say PERI EE
The proportion of apparent D’s to R’s in these offspring
will be
BOSD se 0 (4)
CEE Ds CP TR eoceereeceeeneeereseeosrses .
The remaining equation comes from the offspring of the
apparent Rx R crosses, which give D’s to f’s in the ratio
(p? + 4pq + 3g?) + 2r(ptq) (1 — A) 0: P64 2rq (1 —-8)4
+7r(1— 0),
or say Sen Ge
The apparent offspring will be in the ratio
UO) VO De (5)
"(0 0) SR? :
Statistical examination of families will give in any particular
case the values of the right-hand side of equations (2), (8), (4)
and (5). It remains to determine the ratios p:q:7, and the
value of 6.
with special reference to Right- and Left-Handedness. 511
In the first place it must be noted that it is not in general
possible to satisfy all the five equations (1)—(5) with only three
unknowns, viz. @ and the two ratios p:q:r at our disposal.
Probably the simplest method of attempting to satisfy the equa-
tions is to assume in the first place a value of 6 and substitute this
value for 8 in (2). This gives a linear relation between p, q and r.
Multiply this equation by r and substitute pr=q? from (1), and
we are left with a quadratic equation in - Thus for any assumed
value of @ there will be at most two Se for p:q:7, and it is
an open question whether these values will satisfy the equations
(3), (4) and (5). In fact in the one case in which an attempt to
apply this method has been made it was found quite impossible
to find a value of 6 which would fit into the observed facts, so
long as the more frequent of the two classes observed was assumed
to exhibit the dominant character. Only after a change in the
assumption as to which of the characters was dominant was a
good fit obtained, and then the approximation was very close.
Taking the case of the mode of clasping the hands investigated
by Lutz as a test example, equations (1)—(5) assume the follow-
ing form:
Dig =A pect cake tee (6),
(p+2q)(1-@)+7r@ _ 40 (1)*
AACHEN = AD eee ;
Dd) 578
R 422 Se ee ee ee (8),
D436
R= 5G )
D2
R’ 735 cece eee esses scenes (10).
These equations apply when the condition with the left thumb
uppermost is regarded as the dominant character. Under the con-
trary assumption the fractions in (7 )—(10) would have to be reversed.
Now if we assume a turn-over of 20°/,, due to “accidents,”
from either position, and substitute in (7) 0=0: 2, we get
2p + 4q —r=0,
or multiplying by 7 and substituting from (6)
29° + 4qr — 7? = 0,
ve ge es
r 2
* Lutz gives 61°/, 3s and 58°/, ¢s with right thumb uppermost. We take
60 °/, a8 a mean,
512 Messrs Stratton and Compton, On Accident in Heredity, etc.
Rejecting the negative solution we get i 0:22, and from (6)
F = 0:08.
We may take the numbers 3:14:65 as approximately repre-
senting the ratios p:q:r. Then we get
vet
Rm45,
ae
Ik BO
Di 2
(Re F732
a surprisingly close fit to the observed figures (p. 511).
It is not desired to press this particular case too strongly,
save as affording an instance in which the admission of an
“accidental” factor brings an otherwise discordant inherited
character into harmony with known laws.
* * * * *
The above calculations can easily be adapted to suit cases in
which the reversal of a character only takes place in one di-
rection. Such a case would be that of the functional asymmetry
to which the terms right- and left-handedness are usually applied.
Here the effects of education seem to tend steadily to the con-
version of left-handed persons into right-handed, and probably
never act in the opposite direction.
The object of this note is to show that it is possible, by the
exercise of assumptions which seem to be justifiable, to account
for certain cases to which the usual Mendelian formulae do not at
first seem to apply. The case we have considered specially is an
exceptionally favourable one from the present point of view: for
educational influence seems to be absent; accidental change of
character seems readily to be possible, and would, so far as we
can see, occur with equal ease in either direction.
Mr Campbell, Discontinuities in Light Emassion. 513
Discontinuities in Light Emission. II. By Norman CaAmp-
BELL, M.A., Fellow of Trinity College.
[Read 6 June 1910.]
81. The following pages are a continuation of a former paper
presented to the Society under the same title*. In the former
publication it was stated that the experiments had been un-
successful in attaining their main object: they have continued
unsuccessful.
The difficulty which had prevented the attainment of the
desired results was that of finding a source of light which should
have at the same time great intensity per unit area and great
constancy. The first characteristic was necessary in order that it
might be possible to split the light from the source into two
beams of sufficient intensity by means of an optical system of
lenses and mirrors. The second was necessary because it was
found that the relative intensity of the two beams into which the
light from the source was split changed with a change in the
total intensity of the light. Accordingly, unless the total in-
tensity was quite constant, fluctuations due to alterations in the
total intensity would be imposed upon and would mask the
fluctuations which it was desired to observe.
Throughout the earlier experiments the source of light used
was a Nernst lamp+t. The town supply had been used as a source
of current, and it was thought that the fluctuations in the in-
tensity of the lamp might be due to the changes in the P.D. of
the supply. Arrangements were made to use accumulators as a
source of current, but even with this source the intensity of the
light, as measured by the resistance of the filament, was far too
variable for the purpose of the experiments. The average in-
tensity of the light over a long period was very constant, but
there were considerable fluctuations of short period, which were
probably due to the cooling of the filament by air currents, but
could not be prevented by enclosing the lamp in an almost air-
tight enclosure.
It had been found, on the other hand, that the constancy of
the light from an Osram wire lamp carrying the current from
* Proc. Camb. Phil. Soc. xv. 1909, p. 310.
+ An attempt had also been made to use the sun shining in a cloudless sky as
a source of light, the two beams being divided by means of a half-silvered mirror.
The requisite constancy and intensity appeared to be obtained, so far as could be
judged with the use of the inadequate heliostat which was employed in the prelimi-
nary experiments. But it would be impossible to carry through the research with
such a source of light in aclimate where the necessary conditions are fulfilled so
seldom.
514 Mr Campbell, Discontinurties in Light Emission.
accumulators was amply sufficient for the purpose: preliminary
observations had been made on the fluctuations obtained when
the two photoelectric cells were illuminated by two independent
lamps of this nature, one of which was placed in front of each
cell. But in order that the main experiment might be carried
out, it was necessary to divide the light from a single lamp into
two beams: and such a division was rendered very difficult by the
comparatively large area from which the light was emitted. It
was impossible, for instance, to obtain a parallel beam by means
of a lens and to divide that beam by reflection, as had been
attempted in the case of the Nernst lamp. Since, again, it was
necessary that the two beams, falling on the two cells, should
proceed originally from the same part of the incandescent surface,
it was impossible to obtain such beams as were required by the
simple expedient of placing the lamp between the two cells, so
that light emitted from the lamp in different directions should
fall on the ceils: for, with a wire lamp, the light emitted im
different directions does not come from the same part of the
incandescent filament.
§ 2. An attempt was then made to attain the desired object
by means of the following device. A 110-watt Osram lamp with
a bulb 12 cm. in diameter was silvered thickly on the outside, so
that the walls became very nearly perfect reflectors. Two holes
of 1 cm. diameter were made in the silver, and the light emergent
from these holes was allowed to fall on the two cells. It is easy
to see that the light emerging from either of the holes is made up
of rays emitted from every part of the wire, reflected in most cases
many times from the silvered walls. Accordingly the two beams
emerging from the two holes are “dependent” in the sense of the
word employed in the previous paper. The device was so far
successful that, on looking into the bulb through one of the holes,
no sign of the wire could be seen: the centre of the bulb ap-
peared to be occupied by a uniformly incandescent body, the
shape of which, in accordance with theory, was approximately
that of the surface enveloping the wire filament.
The device was, however, unsuccessful, for the bulb became so
hot that it was necessary to keep it cool by immersion in a water
bath. After a few hours in such a bath the silver began to detach
itself from the walls, whatever method of silvering was used:
covering the silver with several kinds of varnish did not improve
matters materially.
§ 3. An attempt was then made to substitute mercury for
silver. The lamp with the walls carefully cleaned was immersed
in an iron vessel containing clean mercury. Through two holes
in the iron vessel passed two glass tubes with ground ends held
against the surface of the bulb by springs. These tubes provided
Mr Campbell, Discontinuwties in Light Emission. 515
passages for the light through the mercury, and corresponded to
the holes in the silver in the earlier arrangement. The mercury
acted also as a cooling bath, the heat being removed by means of
a stream of water flowing through a jacket covering the top and
surrounding the upper part of the iron vessel. Since mercury is
not nearly so perfect a reflector as silver, the filament could just
be seen on looking in through the tubes, but it could be dis-
tinguished only with difficulty from the bright background
furnished by reflection.
With this arrangement it was found that the relative intensity
of the beams emerging from the tubes, as indicated by the position
of balance of the measuring instrument, did not vary appreciably
with the total intensity of the light. A change of 10°/, in the
current through the lamp was not accompanied by any change in
the position of balance which could be observed. The explanation
of the change in the relative intensity of the beams from a Nernst
lamp with a change in the total intensity of the light was now
obvious. The beams into which the light is divided do not come
entirely from the same parts of the filament, owing to slight errors
in the adjustment of the optical train*. When the resistance of
the filament varies, all parts of it do not undergo the same change
of temperature, and the light emitted by one part of the filament
increases relatively to that emitted from another. But, with the
arrangement now adopted, light from every part of the filament
emerges through both tubes, and changes in the relative intensity
of the light from different parts of the filament have but little
influence on the relative intensity of the light emergent through
the two tubes.
§ 4. But though the main difficulty which had beset the work
hitherto was thus overcome, a solution of the problem had not
been attained. For, when an attempt was made to measure the
fluctuations obtained on balancing the currents through the two
cells, due to the light emergent from the two tubes and incident
upon the cells, it was found that these fluctuations were very
much larger than those which had been obtained under similar
conditions with light from two wholly independent lamps. @7”
was some 12—18 times larger for the two “dependent” than for
the two “independent” sources : and, moreover, the magnitude of
the fluctuations was much more variable, so that it was impossible
to obtain measurements of them which showed any useful agree-
ment. Since on neither of the theories of light which are being
examined the fluctuations due to “dependent” sources should be
greater than those due to “independent,” it was clear that some
important influence had been overlooked.
* See § 19 of the previous paper, where it is noted that the effect depends on the
adjustment of the optical train and not on that of the measuring system.
VOL. XV. PT. VI. 34
516 Mr Campbell, Discontinuities in Light Emission.
A little consideration soon discovered an explanation for the
results obtained so obvious that it ought to have been foreseen.
Equation (9) §7 of the previous paper gives
a= N (w? + 7°),
where a? is the mean square fluctuation in the number of electrons
emitted, V the number of light impulses per second, » the number
of electrons liberated by a single impulse and 7? the mean | square
fluctuation in w. The reason for the very large value of 2 when
the reflecting lamp is used is to be found in the large value of 777.
Some further considerations as to the value of 7? when a plain
open lamp is placed before the cell will be given later. Here it
need only be noted that, in this case, all light impulses which fall
upon the active surface of the cell have very nearly the same power
of setting free electrons. The only variations in this power arise
from slight differences in the distance of different parts of the
filament from the cell, or slight differences in the angle at which
the light from different parts of the filament is incident about the
cell. The greater part of the variation in @ for different light
impulses probably arises from effects connected with the nature
of ionisation: it is unlikely that the value of 7? would be much
reduced if all light impulses had exactly the same power of
forming electrons.
But in the case of the lamp nearly surrounded by a reflecting
surface matters are very different. Part of the light which passes
out through the tubes has travelled a much longer distance within
the bulb than other parts, and has undergone many more re-
flections. Its intensity is reduced both by the increase in distance
and by the loss suffered in reflection by an imperfect reflector.
Even if each point of the filament emits in each elementary cone
light of the same intensity, the intensity of the light emitted from
different points and in different directions will not be the same
when it arrives at the active surface. Accordingly, superimposed
on the variations of w due to variations in the process of ionisation,
there will be variations, probably of far greater amount, due to
variations in the intensity of different light disturbances when
they arrive at the cell.
It would be possible by suitable calculation to obtain some
measure of the amount of the latter fluctuations, but even for
very simple cases, differing considerably from the enclosure of
complex shape which surrounds an Osram lamp, the work is very
laborious and complicated: it has not been thought worth while
to make even an approximation in the absence of any knowledge
as to how close the approximation would be.
We have also to take into account the fact that the convection
Mr Campbell, Discontinuwties in Light Emission. 517
currents in the mercury probably cause slight changes in the
reflecting power of the walls at various points. Additional
fluctuations will be due to this cause, to which may also prob-
ably be attributed the great irregularity of the magnitude of the
fluctuations for the reflecting lamp as compared with those of
the simple lamp. These irregularities are so great that it has
not been thought worth while to give the results of any of the
very large number of measurements which were made on the
fluctuations with a lamp of this nature. In some cases measure-
ments made at different times under apparently similar conditions
differed by more than 100 °/,.
§ 5. When the reflecting lamp proved a failure the ingenuity
of the author was insufficient to devise any new form of source of
light which appeared to offer any reasonable chance of success.
The difficulty which has rendered the experiment impossible was
not foreseen when the work was started, but has proved insuper-
able. Its nature may be described briefly once more.
The object of the experiment was to compare the fluctuations
due to two beams from independent sources, i.e. beams from
different incandescent surfaces, with those due to two beams from
dependent sources, i.e. beams proceeding from the same incan-
descent source and divided, either by being emitted in different
directions or by some such process as partial reflection and trans-
mission. In order to be free from fluctuations due to changes in
the total intensity of the source, either a source of absolutely .
constant intensity must be found, or some means devised of
splittimg the beam in such a way that different parts of it arrive
at the cells without any changes in their relative intensity.
§6. Though the main object of the research had to be
abandoned, some observations were made on the fluctuations due
to independent sources. It was hoped that these might throw
some light, both on the theory of the measurement of such
fluctuations and also, possibly, indirectly on the main problem
which had inspired the research.
The independent sources were two 8-volt 16-watt Osram lamps
placed one opposite each cell. The total intensity of the light
falling on the cell was varied by changing the distance between
the lamp and the cell. Compensating resistances were introduced,
so that a change in the E.M.F. of the battery from which the lamps
were run in parallel did not cause any change in the relative
intensity of the light from the two lamps. The remainder of the
apparatus was exactly as described in the previous paper. The
observations were made and the fluctuations calculated as has
been described with one exception (§ 17). In place of series
consisting of 200 observations, series of 20 observations were
taken. The object of the change was to eliminate errors arising
from the constant drift of the position of balance: it was difficult
34—2
518 Mr Campbell, Discontinwities in Inght Emission.
to obtain series of 200 (13 minutes) without some sign of such
change. Since the calculations gave incidentally a computed
value for the drift, all series were rejected in which that value
showed any material change in consecutive series.
Blank experiments were performed in which the fluctuations
were observed while no light fell on the cells. For such blank
experiments @7? had a remarkably constant value, 0°8 scale
divisions. The value seemed quite independent of the values of
a, b, p, C and R. The fluctuations in such experiments arise
probably from two sources. (1) From the fact that the scale
was read only to the nearest division, so that, even if the spot
was moving perfectly uniformly there would be apparent fluctua-
tions. It is easy to show that for fluctuations arising from this
cause @7? should have the value 4. (2) From chance mechanical.
disturbances in a building which is by no means completely free
from vibration. The independence of the blank fluctuations of
the electrical constants of the system seems to show that electrical
disturbances were sufficiently excluded. A correction equal to the
value of the fluctuations found in the blank experiments was sub-
tracted from all other values of the fluctuations.
It was remarkable that consistent results could be obtained
for the value of the mean fluctuation of less than a single scale
division: but it must be remembered that the means are never
taken for less than 300 observations—sometimes for more than
- 1000.
§7. The first point to be investigated is the variation of the
fluctuations with the intensity of the light: this intensity is
measured by Nw. ‘Table I gives some of the results.
The variation of the fluctuations with the intensity of the
light is important because it might throw some light upon the
two theories, the consideration of which is the chief object of
the work. On the “spherical wave” theory, V, the number of
light impulses falling upon the cell in unit time, is independent
of the distance of the source from the cell: the decrease in
illumination with increase of distance is due to a decrease in ao,
the number of electrons liberated by each impulse. On the
“bundle of energy” theory, it is NV’ which changes with the
distance, while remains constant. Accordingly, if we take
only V and @ into account, equation (9) of the previous paper
shows that on the first theory 67? should be proportional to o?,
i.e. proportional to the square of the intensity of the light, whereas
on the second theory @7? should be proportional to WV, ie. pro-
portional to the intensity simply*.
* A similar argument for the case of y rays has been given by H. v. Schweidler
(Phys. Zeit. x1. 1910, p. 225). The considerations about to be given apply also to
that argument.
a
Mr Campbell, Discontinuities in Inght Emission. 519
But, if we take account of the quantity n?, the matter becomes
rather more complicated. On the bundle of energy theory the
value of 7? is of no importance for comparative measurements,
for » and therefore, presumably, 7? are the same for each bundle,
whatever the intensity of the light. But on the spherical wave
theory the value of 7? is of great importance, since changes in the
intensity of the light are due to changes in the value of o.
The evaluation of 7? cannot be made until some knowledge of
the mechanism by which the electrons are liberated is obtained.
2
But the general theory of probability indicates that - will in-
.crease as w decreases. On two simple assumptions, which give
results that probably differ from the truth in opposite directions,
we can calculate the value of 7% Thus, if we assume that the
light disturbance liberates an electron whenever, in passing
through a layer of constant thickness, it meets a system in some
special condition, it is easy to show that 7?=o. But that as-
sumption involves the conclusion that a single light disturbance
might liberate an indefinite number of electrons, if only it met
a sufficient number of suitable systems—a statement which is
obviously untrue, since the liberation of electrons doubtless re-
quires the expenditure of energy and the amount of energy in
a single disturbance is limited.
Taking an assumption which represents the other extreme, we
may suppose that each disturbance can liberate only one electron,
and that it will only liberate one electron if it chances to meet a
suitable system before its energy is rendered unavailable for the
purpose by passing through the photoelectric layer, or by reflection
or by some other cause. wo is now the chance that a disturbance
will meet such a system before its energy is lost, and a well-
known formula shows that
7? =o(1—«).
Hence on the first assumption
a? = N (w+ o),
on the second assumption = __
2? = No.
In the latter case, whatever the value of w, being, of course,
less than 1, @7” will be proportional to a, that is, to the intensity
of the light, and no distinction can be made between the two
theories. In the former case a distinction can be made only if w?
is not small compared to o.
Now, if Planck’s theory of the “ elementarwirkungsquantum ”
520 Mr Campbell, Discontinuities in Light Emission.
be accepted (and its author holds it to be compatible with the
spherical wave theory), the measurements on the photoelectric
effect in zinc, quoted in the former paper, indicate that the
number of electrons which can be liberated from zinc by a single
light disturbance is about 3, and the number of such electrons
is likely to be of the same order of magnitude in the case of the
alloy of sodium and potassium. But, on the same theory, the
fraction of that number which are liberated within any given
photoelectric cell is the solid angle subtended by the surface of
the cell at the source.
In our case this solid angle was never as much as 4, and
hence, on this theory, w should be considerably less than unity
and 7? large compared with w. It should be expected therefore
that, whichever of the two theories of light emission is true,
Or? should be proportional to the intensity simply. If Planck’s
theory be not accepted, there is no apparent method of calculating
the number of electrons liberated by a single disturbance.
TABLE I,
160 volts on Electrometer Needle. 7% and & are given in electro-
static units, 6,” in scale divisions. The value of the last quantity is
deduced from not less than 300 observations in each case.
(A) R=0:155
i = 89 54 38 26
On? == 1-4 116 75 4:4,
O7?/i = 0-240 0-233 0-197 0-169
677/22 = 0-0027 0:0043 0-0052 0-0065
(B) R=0-205
i = 88 40 26
OPP BOs 15:1 9-1
O7?/i = 0°335 0:375 0-350
6,7/2 = 00-0038 0:0094 0:0134
(C) R=0:304
i = 86 49 29
6,7 = 501 24-8 15-2
Ot = 0-584 0506 0-529
677/2 = 0:0068 0:0103 0:0180
Mr Campbell, Discontinuities in Light Emission. 521
2
It will be seen from Table I that the value of 07? varies
apparently as some power of the intensity between the first and
the second, but considerably nearer to the first. This result
shows that, contrary to the hopes of the author, no evidence has
been produced against the “spherical wave” theory. Indeed the
fact that the power of the intensity is slightly greater than unity
might be held to be favourable to that theory as opposed to the
“bundle of energy” theory. But it must be remembered that all
sources of error tend to increase the fluctuations at the higher
intensities in comparison with those at the lower and so to give
a divergence from a proportionality between @7? and the intensity
in the direction observed.
In the first place there is a possible error from small changes
in the magnitude of the constant “drift” of the position of balance,
which increases rapidly with the total intensity of the light falling
on the cell. The cause of the drift was never discovered. It was
always, on the average, in the same direction while the light was
acting, and may probably be due to some slight “ photoelectric
fatigue,” notwithstanding the high vacuum, which was different in
the two cells.
In the second place the considerations mentioned in § 5 above
must be remembered. The finite area of the source of light is of
less importance when the source is further from the cell: hence
9? is likely to be somewhat less at greater distance.
It is concluded, accordingly, that these experiments can make
no decision between the two theories: they can only say that the
“spherical wave theory” is inconsistent with a large value for o—
a conclusion which is to be expected on other grounds.
§ 8. The second point requiring consideration is the variation
of the fluctuations with the instrumental constants. ‘These con-
stants were altered in two ways:—(1) By changing the potential
of the electrometer needle and so altering at the same time the
electrometer constants a and 0b, the sensitiveness s and the
capacity C. (See previous paper.) (2) By changing the re-
sistance R.
(1) Table II shows the calculated and observed values of the
ratios of O7? for different values of the potential on the electro-
meter needle, the resistance being kept constant during any one
set. a@ and b were never less than six times p: hence the ex-
pression (11’) of the previous paper reduces without sensible
error to
ease
T
() Pr Odt= 55.
It will be observed that the agreement between calculation
and observation is quite as good as could be expected. Since the
522 Mr Campbell, Discontinuities in Light Emission.
period of the electrometer varied in the ratio of 2°5 to 1, it is clear
that the prediction of theory that the fluctuations are independent
of the period of the measuring instrument, so long as it is suf-
ficiently small, is justified.
TABLE IT.
V is potential on electrometer needle, s sensitiveness, C capacity ;
6;* is in scale divisions, deduced from not less than 300 observations
in each case.
Ratio Ratio a Mean
of of ee ee ae ratio
Vi 3 C (R=0-304 0-336 0:0316) _—eale. obser.
160 1-00 1-00 16-0 15°6 5:3 1:00 1-00
120 0:52 0°81 9-2 12-0 3'1 0-64 0-66
80 0-24 0-64 o-4 7:0 19 0°37 0°39
(2) Table III shows the variation of @7? with p, when p is
changed by alterations in the resistance R. Only one set of
measurements is given, but other sets with other values of the
remaining constants show exactly similar features. The last
column gives the value of the quantity which should be constant,
if the theory which has been given is correct: it will be observed
that it is approximately constant for the higher values of A, but
shows a marked increase for the lower values.
TaB_e III,
160 volts on electrometer needle. s=gx 10°, 2= 84.
R Cc On? Oy". R/2C
0-336 395 52-0 1:22 x 10°
0:304 410 50-9 1:34 x 10°
0-205 400 29-5 1:18 x 10°
0-155 405 21-4 1:12 x 105
0-110 460 22-0 1°84 x 10°
0:096 520 17:2 1-86 x 10°
0:032 710 ES 3:15 x 10°
0:027 750 4-9 2-73 x 10°
$9. The explanation of this deviation from theory has not been
discovered, but it appears to be connected with an increase in the
measured capacity of the system with a decrease in resistance, a
change to which reference was made in the previous paper. The
resistance # was measured by passing a known current through
4
Mr Campbell, Discontinuities in Light Emission. 523
the resistance and measuring the potential difference between its
ends. The quantity p, the logarithmic decrement of the charge
on the electrode system, was found by observations on the decay
of the deflection of the electrometer needle: the capacity was then
found from the relation C= = Measurements made in this way
showed that the capacity of the electrode system increased notably
with a decrease of R, while it was expected that C would be almost
independent of R. The only change made in the apparatus when
R was altered consisted in a change of the distance apart of the
electrodes immersed in the high resistance fluid, and the calculated
capacity of these electrodes at their nearest approach was only
15 cms., less than 4, of the whole capacity. Moreover, it was
found that a variation in the resistance made no difference in
the ratio of the capacities of the electrode system with different
potentials.on the electrometer needle: it would seem then that
the change of capacity must lie in the electrometer and not in the
rest of the system.
When the resistance was sufficiently high, or when additional
capacities were inserted, measurements could be made of the
capacity by other methods. In all cases these agreed with the
capacities measured by the decrement method: but in those cases
when the measured capacity appeared abnormal, when measured
by the decrement method, no other method of measurement of
sufficient accuracy could be devised, whereby the results might be
checked.
§10. It will be observed that, if the theory of the measure-
ments which has been given is correct, a knowledge of the number
of electrons liberated by a single light disturbance can be found
from the relation
nf se 2pC?
(o+7) a: eis? ”
where 7 is the total photoelectric current.
In making use of this relation, only those observations made
with resistances greater than 0°15 have been used: it has been
assumed, for the reasons given at the end of the last paragraph,
that the values for smaller resistances are abnormal. The mean
2
value of (+7) is then found to be 41, if the value of e, the
charge on an electron, is 465 x 10-™
The resulting value of w depends on the assumptions made in
calculating 7. It will be seen that the value is inconsistent with
the second assumption made in § 7, when discussing the value of
this quantity, for on that assumption » could not be greater
524 Mr Campbell, Discontinuities in Light Emission.
than 1. On the first assumption, which leads to ?= a, the value
of @ is 3:1, a quantity which agrees well in order of magnitude
with that found by totally different experiments. (See §7.) It
also agrees, at least so far as order of magnitude is concerned,
with that to be expected from Planck’s theory of radiation, if, and
only if, the bundle of energy theory is true. If the spherical
wave theory is true, and the energy in a single light disturbance
is spread over a sphere surrounding the source, the above value
for » must be multiplied by more than 100 in order to take
account of the angle subtended at the source by the photoelectric
cell.
It appears to be the chief importance of this work that it
has shown that it is possible, by the fluctuation method of
v. Schweidler, to obtain directly measurements of quantities
agreeing well with those deduced on other and much more
indirect methods.
Summary.
1. The paper is a continuation of that presented lately to the
Society under the same title. The difficulties which had hitherto
prevented the attainment of results are described.
2, 3. A description of new sources of light designed to over-
come these difficulties, and an explanation of their nature.
4. Reasons are given for the failure of the new devices to
attain the desired object.
5. With this failure all hope of carrying out the main purpose
of the research was abandoned.
6. It was thought, however, that some results of value might
be obtained by the observation of the fluctuations of two indepen-
dent sources of light. The method of measurement is described.
7. The variation of the fluctuations due to such sources with
the total intensity of the light is first examined. It is pointed
out how far such measurements could be used to distinguish
between the rival theories of light. The conclusion is reached
that the experiments recorded here afford no grounds for dis-
tinguishing between these theories. They can only fix a limit
to certain values which is in accordance with deductions from
other work.
8,9. The variation of the fluctuations with the instrumental
constants is examined. It is concluded that the agreement
between experiment and the theory worked out in a previous
paper is satisfactory, except in cases where the value of the
resistance R is small. Reasons are given for thinking that these
Mr Campbell, Discontinuities.in Light Emission. 525
values are abnormal, and that the theory of the measurements
may be held to be established for the larger resistances,
10. If the theory of the measurements examined in § 8, 9
is accepted, the observations lead to an estimate of the average
number of electrons liberated by a single light impulse. The
number obtained is 3:1. This result agrees well with that which
has been deduced on other grounds, and also with that to be ex-
pected from Planck’s theory of radiation, if the bundle of energy
theory is correct.
526 Mr Wilks, The Absorption of Bromine by Lime.
The Absorption of Bromine by Lime. By W. A. R. WILKS, B.A.,
Gonville and Caius College. (Communicated by Dr Fenton.)
[Read 23 May 1910.]
The action of bromine on slaked lime was first investigated by
Berzelius. The product obtained—often called “ bromine-bleaching
powder ”’—appears to have been very little studied since. Owing
to the fact that many adsorption compounds, as in the well-
known instance of iodide of starch, have peculiar colours it was
suspected that this might be a similar case. The product has a
reddish brown colour, and as this appears to be anomalous, at
Dr Fenton’s suggestion the author undertook an investigation on
the subject.
A series of experiments was carried out in the following way.
A gram of pure freshly prepared slaked lime (dried in a vacuum
desiccator) was weighed into a stoppered glass bottle and 100 cc.
of a carbon tetrachloride solution of bromine (of known strength)
added. Solutions of different strengths were added to the same
quantity of lime in other bottles, the volume of solution being
always 100 cc. After equilibrium was attained the strengths of
the solutions were determined by means of potassium iodide. The
concentration of bromine in the lime was then calculated. The
following are some of the results obtained.
10 c.c. of bromine solution Amount of bromine in 1 gm.
required in c.c. of of lime expressed in terms
‘thio ” of ‘ thio” solution
4-45 44-6
13-2 46:2
22°05 46°8
31:05 46:0
39°85 47:0
The thiosulphate contained ‘02108 grm. of Na,S,O, per c.c.
Temperature of experiment 15°C. In this experiment the con-
centration of: bromine in the lime was constant while the concen-
tration in the solution varied. The most probable interpretation
of this result is that a chemical compound is formed, probably
analogous to bleaching powder. The ratio Ca (OH), : Br = 4°42 : 1.
Much weaker solutions of bromine were used in the next
experiments which were carried out in the same way as before.
Mr Wilks, The Absorption of Bromine by Lime. 527
10 t.c. of bromine Amount of bromine in
solition required 1 gm. of lime expressed Cy
: f cae ” in terms of ‘‘ thio” Taal
mone C. i solution C28
=O oe
ie 42:6 2-443
te 50-2 2-130
21°8 68-2 9-44]
30°6 76-4 9-443
10 c.c. Iodine solution (1 ¢.c, = 01282 I) =51°85 «ec. “thio.”
Here the concentration of the bromine in the lime increases
with the increase in concentration in the solution. The third
1
column gives the numbers calculated from the expression =—
2
when n is made one-third. These numbers are sensibly constant.
This result might be explained either by assuming that the
bromine is in solid solution in the lime or that it forms an
adsorption compound. On the first hypothesis the bromine in
solid solution would be dissolved as a fraction of an atom (assuming
that bromine in carbon tetrachloride dissolves as Br,—a most
probable assumption since iodine has been shown to dissolve in
the same liquid as I,). It seems fairly certain therefore that we
are dealing with an adsorption phenomenon.
In both the above experiments the slaked lime was freshly
prepared from pure quicklime and dried in a vacuum desiccator
for two days. In the following experiment it was dried for four
weeks.
10 c.c. of bromine solution Amount of bromine in 1 gm.
required in c.c. of of lime expressed in terms
“thio” of ‘‘ thio” solution
2°48 22°66
6°85 26°42
11:70 35°38
25°35 31°16
34°55 34:18
44-0 34:60
53°6 33°52
37°2c.c. of “thio” = 10 c.c. Iodine solution (1 c.c. = ‘01282 I).
528 Mr Wilks, The Absorption of Bromine by Lime.
In this case when the concentration of the bromine in the
solution is small the bromine is adsorbed by the lime, but the
concentration of bromine in the lime soon reaches a constant so
that it is not possible to calculate the values — The constant
12
concentration of bromine in the lime again indicates the formation
of a chemical compound. The ratio Ca(OH),: Br=149:1. The
drier the lime therefore the less the ratio Br : Ca(OH), becomes—a
result quite similar to that obtained by other observers in the case
of chlorine and lime.
In the last experiment the colour of the lime deepened from
yellowish brown to reddish brown as the concentration of bromine
in it increased. After a constant concentration was reached the
colour was unaffected by increasing the concentration of bromine
in the solution.
Messrs Jones and Matthews, Reduction of Nitrosyl Chloride. 529
Note on the Reduction of Nitrosyl Chloride. By H. O. JONEs,
M.A., Clare College, and J. K. Marruews, B.A., Downing College.
[Read 23 May 1910.]
While examining the interaction of nitrosyl chloride and
ethyl mercaptan in ethereal solution at — 80°C. the formation
of small quantities of hydroxylamine hydrochloride was observed.
This was produced by the reducing action of the mercaptan on
nitrosyl chloride with the simultaneous formation of diethyl
disulphide.
The action of other reducing agents on nitrosyl chloride was
therefore studied.
Hydrogen sulphide and nitrosyl chloride, in the presence of an
inert solvent such as ether or petroleum ether, interact to produce
ammonium chloride and sulphur even at low temperatures. Some
sulphur chloride is also produced, but this was found to be due to
the action of nitrosyl chloride on the sulphur formed by the first
action.
The main reaction may be represented by the equation
NOC! + 3H,S = NH,Cl + H,0 + 38,
though attempts to establish this by quantitative experiments
were not successful owing to the secondary reactions which take
place.
In the gaseous state nitrosyl chloride and hydrogen sulphide
interact to produce sulphur, together with some sulphur chloride,
hydrochloric acid, nitric oxide, nitrogen and ammonium chloride.
Under no conditions was the formation of hydroxylamine
hydrochloride observed.
The action of hydrogen on nitrosyl chloride in the presence
of palladium, of finely divided platinum and of nickel was next
examined.
At the ordinary temperature palladium charged with hydrogen
was attacked by nitrosyl chloride with the formation of palladium
chloride, nitric oxide and nitrogen.
When hydrogen and nitrosyl chloride were passed over palla-
dium at temperatures between 100° C. and 230° C. the ‘palladium
was not appreciably attacked and considerable quantities of ammo-
nium chloride were produced, but no hydroxylamine hydrochloride
could be detected in the product.
A mixture of nitrosyl chloride and hydrogen was then passed
over finely divided platinum, prepared by the reduction of platinum
530 Messrs Jones and Matthews, Reduction of Nitrosyl Chloride.
chloride by means of an alkaline solution of glycerol. At the
ordinary temperature a very vigorous reaction set in at once, the
temperature of the platinum rose rapidly to a red heat and
ammonium chloride was formed.
The platinum was therefore surrounded by a freezing mixture
and the gases allowed to pass over it very slowly, and in this way
some hydroxylamine hydrochloride was formed together with the
ammonium chloride, but the quantity was small, hardly exceeding
five per cent. of the ammonium chloride formed. Nitrogen was
also produced. : ,
Nickel was also found to bring about the interaction of
hydrogen and nitrosyl chloride with the formation of ammonium
chloride.
Messrs Strickland and Swellengrebel, Trypanosoma lewisi. 531
The development of Trypanosoma lewisi in the Rat Flea
(Ceratophyllus fasciatus). By C. STRICKLAND, B.A.,and Dr N. H.
SWELLENGREBEL. (Communicated by Prof. Nuttall.)
[Read 6 June 1910.]
Little is known about the development of trypanosomes
outside the vertebrate host, and what is known is lable to
Patton’s criticism, that asserts that most of the Crithidia forms
found in different invertebrates and considered to be develop-
mental forms of various trypanosomes are indeed independent
forms and have no connection’ with trypanosomes.
This question being of the highest importance not only
theoretically but also from a practical point of view in con-
nection with sleeping sickness, we endeavoured to trace out the
life-cycle of J. lewist (provided there were any) in the rat flea
(Ceratophyllus fasciatus). We chose the rat flea and not the
louse (Haematopinus spinulosus) because it is clear from the
papers of Nuttall, Manteufel, Minchin and one of us (C. 8.) that
the louse transmits the trypanosomes only mechanically, whereas
the flea becomes infective after 7—14 days and remains so for
ee time, which fact suggests that a true development takes
place.
We infected 83 fleas out of an uninfected lot (bred in the
laboratory), allowing them to feed during a period of 12 hours
upon an infected rat (10th day of infection). The fleas were
then removed from the rat and were fed at intervals of three days
by biting non-infected rats through a gauze bag. A control series
of experiments was made by feeding 60 fleas (out of the same box
as the infected series) on a non-infected rat and by treating them
afterwards in the same way. Each day, for 16 days after the first
feeding, four to six of the infected and control fleas were dissected
and observations were made in vivo and in stained preparations.
The control fleas were not always free from flagellated forms.
Nothing was ever seen in the living preparations; but by making
stained preparations of the different parts of the gut, we were able
to detect flagellates in 3°3°/, of the fleas. This fact was probably
due to an accidental infection, an infected rat having broken into
the flea box. But even if we consider the flagellates of the control
fleas to be natural forms, we may safely conclude that most of the
flagellates found in the fleas fed on infected rats are developmental
stages of 7’. lewist, because the rate of infection was 44°/,.
VOL. XV. PT. VI. 35
532 Messrs Strickland and Swellengrebel, The development
Twelve hours after feeding on the infected rat, 7. Jewist may
be found unaltered in the midgut, after 24 hours the blepharoplast
leaves its terminal position and approaches the nucleus. The
hind-end of the flagellate becomes larger so that the trypanosome
appears club-shaped. The nucleus now wanders to the hind-end
of the flagellate, and consequently the distance between the
blepharoplast and nucleus diminishes gradually, and at a later
stage the two pass each other so that the blepharoplast is situated
in front of the nucleus, the trypanosome having now a Crithidia
facies. This change is accomplished in the midgut in 14 days.
The club-shape is now very well marked and the front-end of the
flagellate becomes thinner and thinner, the flagellum often staining
with difficulty. At last the flagellar end of the parasite atrophies,
and the trypanosome is now metamorphosed into an oval-shaped
cell, with a short flagellum, the blepharoplast being situated at
the side or in front of the nucleus. These “large oval forms,” as
we may call them, pass into the anterior part of the hindgut,
and are to be found there after 34 days in rosettes. During the
following days the large oval forms become rounded, giving rise to
the so-called “round forms,” which begin to divide actively after
5—6 days. This development is first to be observed in the flea’s
rectum but afterwards also in the hindgut. We never observed
any indication of multiple division, but the parasites arising from
the repeated binary division of the round forms hold together with
the front-ends, so that rosettes are formed. These rosettes are
composed of “little oval forms” with short flagella, the blepharo-
plast being situated just in front of the nucleus. Gradually these
become more elongated, the flagellum grows out further, and
the blepharoplast passing the nucleus comes to lie in the posterior
end of the cell. Since the flagellum follows the blepharoplast, the
result is the formation of an undulating membrane. The parasite
has now recovered the aspect of a small trypanosome with a
particularly large blepharoplast, situated at the extreme posterior
end. These forms begin to appear after 7 days but are abundant
after 8—10 days and remain so for an indefinite time, probably
till the host’s death.
All these different types of parasites—little ovals, intermediate
Crithidiae and small trypanosomes—may divide, so that prepara-
tions made during the last stage of infection exhibit a great
variety of forms. The small trypanosomes and the Crithidiae
from which they originate occur in two well-marked types: a
slender one and a stout, but united by intermediate forms. We
do not know if this is to be considered as a sexual differentiation,
but we have never seen any sign of conjugation.
Not being able to find any further stage of development
beyond that of “small trypanosomes,” either in our series or in
of Trypanosoma lewis, in the Rat Flea. 533
the fleas taken haphazard from infected rats, we think it possible
that these forms represent the final stages of development. If so,
we are unable to say in which way these small trypanosomes
return to the rats’ blood. We have not been able to find any
flagellated form either in the coelom or salivary glands of infected
fleas.
At present the broad fact remains established by a proper
system of controls that 7’. Jewisi undergoes a morphological cycle
of development in the gut of its invertebrate host.
35—2
534 Mr Brooks, The Development of Gnomonia erythrostoma,
The Development of Gnomonia erythrostoma, the Cause of Cherry
Leaf Scorch Disease. By F. T. Brooxs, M.A., Emmanuel College.
[Received 6 June 1910.]
[ Abstract. ]
The life-history of this Pyrenomycete may be summarised
as follows: Infection of the foliage occurs in the early summer
by means of the ascospores. Spermogonia and “coils” are formed
in the diseased leaves. It was considered by Frank, whe described
the outlines of the life-history several years ago, that the spermatia
produced in the spermogonia fertilise the “coils” by passing down
the trichogynes which arise in association with the latter. The
“coils” ultimately develop into perithecia. During the summer
the vegetative mycelium passes down the leaf stalk and prevents
the formation of the absciss layer. On account of this, the diseased
leaves remain hanging on the trees throughout the winter and
become the source of reinfection the following season.
The present investigation concerns an examination of the life-
history of this fuugus from the cytological standpoint, very little
work on the Pyrenomycetes having hitherto been done from this
point of view.
The vegetative mycelium of Gnomonza consists of multinucleate
cells. It is intercellular and haustoria are not developed.
The spermogonia show similarities in structure to those of the
Uredineae. The spermatia are long and thread-like and exhibit
the cytological characters of male cells. It is considered, however,
that they are now functionless, there beg no evidence that
fertilisation is effected by their agency as Frank supposed was the
case.
The trichogynes occur in tufts of 2—5. They do not in-
variably arise in association with “coils.” It is suggested that
the trichogynes though originally receptive organs now perform a
different function—serving possibly as a means of aeration.
The “coils” represent the first stages of perithecial develop-
ment. In the centre of each coil one or more slightly differentiated
hyphae are found. These are considered to be of the nature of
ascogonia. No clear connection can be traced between the
trichogynes and these cells. The “coil” undergoes a period of
rest before developing further.
the Cause of Cherry’ Leaf Scorch Disease. 535
In the subsequent stages of development of the perithecium
from the “coil” it is no longer possible to trace the ascogonia.
There is evidence to show that the ascogenous cells arise by
differentiation from ordinary cells. No fusion of nuclei has been
observed prior to that which occurs in the young ascus.
The nuclear phenomena in the ascus are described in some
detail. Only a single process of reduction has been observed
which occurs at the time of the first nuclear division. It is not
possible yet to decide whether this division is heterotypic or
brachymeiotic though the analogies are with the former rather
than the latter.
Thus only a single nuclear fusion and a single process
of reduction have been seen to occur in the life cycle of this
Ascomycete.
5386 Dr Cobbett, The Absence of Lnving Tubercle Bacall
The Absence of Living Tubercle Bacilli from some Old Tuber-
culous Lesions in Man. By Louis Copsett, M.D. Pathological
Laboratory.
[Read 6 June 1910.]
Two theories of the origin of phthisis involve the hypothesis
of latency—Baumgarten’s which regards infection as occurring
before birth, and remaining undeveloped, perhaps for years; and
Behring’s which regards infection as occurring usually during
infancy, and remaining latent until some disturbance of health
set up by the onset of puberty, by parturition or lactation, or by
measles or some other of the specific fevers or some other cause
weakens the natural powers of resistance and so favours the
growth of the bacilli. “Then,” to translate Behring’s words, “we
have the beginning of phthisis, but the real origin of the tuber-
culous infection is far back.” Both theories then assume that the
tubercle bacillus is capable of remaining alive quiescent in animal
tissues for long periods of time, measured not by weeks and months
but by years.
Behring in arriving at his views was largely influenced by the
frequency with which lesions apparently tuberculous are found,
often quite unexpectedly, in the bodies of those who die from all
sorts of causes.
These lesions undoubtedly occur very frequently, though
opinions may differ as to just how common they are. The
difference of opinion is due to the difficulty of deciding im some
cases whether the lesion is tuberculous or not. But in many cases
there is no difficulty at all, there is definite caseation or calcifica-
tion, and in some the characteristically acid-fast tubercle bacilli
may even be seen under the microscope. In such cases very little
attention seems to have been paid to the question whether the
lesion was really quiescent, or healed, that is to say whether it
did or did not contain living bacilli capable under favourable
conditions of causing a tuberculous infection.
During the time when I was working for the Royal Com-
mission on Tuberculosis I was more than once astonished to find
that what I regarded as undoubtedly tuberculous material had
no effect when injected into the guinea-pig; and, as this is one of
the most sensitive of animals to tuberculosis, whether caused by
bacilli of the human or bovine variety, I could not but regard
the lesions from which this material had come as cured, that is to
say incapable of giving rise to any further tuberculous trouble.
Since I left Stansted I have continued to investigate isolated
and unsuspected tuberculous lesions, which have been from time to
from some Old Tuberculous Lesions in Man. 537
time found in the bodies of those who died from other causes, and
not a few of these have been found to be non-infective. These ob-
servations seem to me to be worth recording as a contribution to
the data from which one may estimate the duration of the vitality
of tubercule bacilli in the bodies of living animals, and because
our views about the practically important question of the origin of
phthisis must be largely determined according to the conclusion
we come to as to the vitality of the bacillus. If any considerable
proportion of these lesions are really not capable of infecting then
the great frequency with which they are present is not so strongly
in favour of latency as it is usually held to be.
The first case investigated by me was that of a child of eight,
who died of diphtheria. Quite unexpectedly, at the post-mortem
examination, was found a mass of enlarged mesenteric glands, four
of which were caseous and softened at their centres. There was
ample material for the purpose of inoculation and I was able to
make as much as 25 cc. of a creamy emulsion, in which as many
as 170,000 tubercle bacilli per cubic centimetre could be seen.
The whole of this emulsion was injected into two calves, two
rabbits and two guinea-pigs, but not even the latter developed
any trace of tuberculosis.
Naturally I considered the result suspicious, and every: sug-
gestion probable and improbable was considered which might
account for it, without having to suppose that the bacilli were
dead; but without success. It was even thought that diphtheria
toxin might be fatal to tubercle bacilli, but this was tried and
found not to be the case.
The next case was one in which tuberculous glands were re-
moved by operation from a child of a little under four years of
age. Fifteen months previously some glands had been removed
from this child and sent to me, and proved to contain numerous
virulent tubercle bacilli of the bovine type. The glands removed
at the second operation contained two as large as ripe gooseberries,
which were caseous and softened. An emulsion was made in the
usual way and injected into guinea-pigs, but the animals remained
unaffected, and cultures attempted from the emulsion failed to
grow any tubercle bacilli.
The next case was one of tuberculosis mainly affecting the lungs
and pleura of a child of eight. The bronchial glands were en-
larged, and three contained small caseous foci, another contained
a larger mass of the same material; a guinea-pig injected with
all the caseous material which could be obtained from these glands
remained unaffected. No tubercle bacilli were seen in the emulsion
prepared for injection.
The fourth case was one of localised tuberculosis in a boy of
fourteen. After a slight injury to the hand, which was slow in
538 Dr Cobbett, The Absence of Living Tubercle Bacilla
healing, an almost painless slowly growing lymphatic gland ap-
peared in the axilla, and about two months later it ulcerated
through the skin and discharged a thin fluid. Some of this
discharge was used for the injection of guinea-pigs but without
effect. The quantity of it was small, but its tuberculous nature
was demonstrated by finding a few tubercle bacilli in it.
The fifth case occurred in Sheffield. It was clinically a typical
case of Addison’s disease, in a young woman. No trace of the
supra-renals could be found though carefully sought for, and no
lesion of any kind was found, except a single mesenteric gland of
stony hardness and entirely calcareous. No tubercle bacilli could
be found in it by microscopic examination. The gland was
emulsified and injected into guinea-pigs but no tuberculosis re-
sulted. They were killed two months later and traces of the
material injected were found bound to the omentum, but no
tubercle bacilli could be found in this material and there was
no cellular action around them.
In the next two cases living tubercle bacilli were found in the
old lesions.
The sixth case occurred in Cambridge, it concerned a child of
four who had tuberculous disease of the upper dorsal vertebrae.
An abscess formed in the thorax which interfered with respiration,
and the child died. At the post-mortem examination an old
caseous mesenteric gland was found. It was about ? of an inch
in diameter and consisted of thick gritty caseo-pus contained
within pink-coloured fibrous walls.
Two guinea-pigs were injected with the caseous material, one
developed tuberculosis, the other did not.
The seventh case, a youth of eighteen, died of heart disease.
A caseous bronchial gland, as large as a bean, and filled with
creamy caseous contents containing calcareous grains. No tubercle
bacilli were found in it by microscopic examination, but it caused
tuberculosis when injected into guinea-pigs.
Among these seven cases were five in which material which
I think may be regarded as undoubtedly tuberculous was injected
into guinea-pigs without producing tuberculosis.
Similar observations have been made by those working for the
Committee of the Kaiserliches Gesundheitsamt, appointed to in-
vestigate the relation of bovine to human tuberculosis. It cannot
be doubted then, I think, that tuberculous material taken from
man is sometimes incapable of causing tuberculosis in susceptible
animals. And it seems a fair inference that it contains no living
bacilli.
It may perhaps be argued that these lesions were not really
tuberculous, but this can hardly apply to case No. 2. And if
these caseous and calcareous glands were not tuberculous what
from some Old Tuberculous Lesions in Man. 539
were they? Some of them undoubtedly contained acid-fast
bacilli.
It may again be suggested that even the guinea-pig is not
entirely devoid of the power of resisting tuberculous infection,
and to some extent can get over small doses of bacilli, as the calf
and other animals, including man, undoubtedly can, and that in
these cases the dose was too small to infect. To this it may be
replied that doses apparently equally small have frequently been
given with positive results, and that in some of the cases recorded,
notably the first, the dose cannot be considered small since many
thousand tubercle bacilli were present in each cubic centimetre of
the emulsion injected.
I do not propose to discuss now the vitality of tubercle bacilli
in actively living tissues—hitherto we have been considering their
vitality in necrotic tissue caseous and calcareous. Many observers
have found living tubercle bacilli capable of infecting guinea-pigs
in enlarged tonsils, adenoid vegetations, or in cervical, mesenteric,
or bronchial lymph glands. Work of this kind carried out by
Weber and Baginsky for the Committee of the Gesundheitsamt,
however, shows that such infection is not very common. More-
over, as these authors remark, one cannot tell in these cases how
long the bacilli have been there. They might conceivably have
only just got into the tonsil or lymph gland in which they were
found.
If it is worth while speaking at all of probabilities, it seems
hardly likely that bacilli could survive in living tissues which we
know possess some degree of bactericidal power longer than in
inert, dead, caseous, or calcareous matter.
Again it seems improbable that tubercle bacilli should remain
alive in a quiescent state for great lengths of time. It is generally
conceded that they do not form spores, and in our artificial
cultures their vitality is measured by months rather than by
years.
Very many more observations are needed before we can form
any opinion as to the frequency with which living tubercle bacilli
are present in old and quiescent tuberculous lesions. I have
brought forward these few because much time must necessarily
pass before I can greatly enlarge the number, and because few as
they are they make one question, whether the frequency with
which old tuberculous lesions are met with in post-mortem
examinations really lends so much support to the hypothesis of
latency as it is usually held to do.
540 Mr Satterly, Radvum-content of Cambridge Waters.
Note on the Radium-content of the Waters of the Cam, Cam-
bridge Tap Water and some varieties of Charcoal. By JoHNn
SATTERLY, B.A., B.Sc. (Lond.), St John’s College. (Communicated
by Professor Sir J. J. Thomson.)
[Received 24 June 1910.]
In view of the fact that the author has found more radium
emanation in the air at Cambridge* than Eve found in the air at
Montreal + it was thought that it would be of interest to examine
quantitatively the water of Cambridge for radium.
Some experiments have already been made on the radio-
activity of Cambridge tap water. J. J. Thomson} showed that
air bubbled through this water became radioactive due to the
removal from the water of some dissolved gas. Adams§ tested
this gas and identified it with radium emanation. He also
established that the water contained dissolved radium as well,
for after boiling the water and clearing out the dissolved: emana-
tion a little emanation accumulated when the water was allowed
to stand for some days; he states that the recovery was about
one-tenth of its previous value. Adams evaporated quantities of
water to dryness but failed to find any activity in the residue.
Strutt|], who employed Cambridge tap water in the aspirators
which he was using in his work on the estimation of radium in
rocks, states that no measurable quantity of emanation was
generated in the water which had been previously boiled, although
a close examination of his figures shows that two litres of water
generated in a fortnight enough emanation to send up his air-
leak about 4°/,. None of the above experimenters however had
at the time the means of expressing the amount of emanation in
terms of the mass of radium which would generate it.
Recently Eve{l has examined the water of the St Lawrence
which is delivered as the town supply of Montreal without any
filtration or other treatment, and found its radium-content to be
‘25 x 10-” gm. of radium per litre of water, and Joly has found for
the Nile 42 x10—% For sea-water from the North Atlantic,
Eve] has found on the average ‘9 x 10-” gm. of radium per litre,
* Phil. Mag. Oct. 1908 and July 1910.
+ ibid. Oct. 1908.
+ ibid. Sept. 1902.
§ ibid. Nov. 1903.
|| Roy. Soc. Proc. A, Vol. uxxvi1. 1906.
{| Phil. Mag. July 1909.
Mr Satterly, Radium-content of Cambridge Waters. 541
and Joly 16 x 10-”*, and more recently 12 x 10~-"+ as an average
of sea-water from all over the world.
The method of testing in my experiments was to take the
water straight from the Cam or the tap and boil it in a flask
connected to a condenser and aspirator. When the water was
boiling air was rapidly drawn through it by the aspirator; the
emanation was thus withdrawn and collected in the aspirator.
The steam condensed in the condenser and ran back into the
flask. The emanation-charged air in the aspirator was then passed
into a previously exhausted testing vessel and the leak taken.
This leak less the normal air leak is a measure of the emana-
tion.
The waters of Cambridge contain much chalk in solution, so
that unless acidified a deposit occurs on boiling. As this might
affect the quantity of emanation given off two samples of each
water were tried, one untouched and the other acidified with a
little hydrochloric acid (the acid itself was tested and though not
free from radium yet would, as only a small quantity was used
contribute practically no emanation, see Table IT).
In the first set of experiments a litre of water was taken each
time, and when acidified two cc. of acid was used. After each
boiling the flask was corked up and allowed to stand for any
emanation to accumulate when the water was again reboiled and
the emanation drawn off and tested. It was found that practically
no emanation was accumulated on resting, so that practically all
the emanation initially present in the water is just dissolved
emanation.
Table I gives the first set of results; the amount of emanation
being expressed on an arbitrary scale (the numbers are the leaks
per minute in the testing vessel as read on the scale provided to
the electrometer. The air leak which was about 1:0 has already
been subtracted).
f)
TABLE I.
Cambridge tap water (one litre). Cam water (one litre).
A t of A t of
Treatment Sila naiein Treatment Sas:
(1) No acid added 9-0 (4) No acid added “4
(2) 2cc. HCl ,, 9-0 @)l Beene + 6
(2p Sol i ile ls (6) Noacid _,, 2
* Phil. Mag. May 1908. + ibid. Sept. 1909.
542 Mr Satterly, Radium-content of Cambridge Waters.
(1), (2), (8) were collected on separate days, (4) and (5) were
collected at different times on the same day from the Cam at
Sheep's Green just above the flood-gates, and (6) on another day
from below the flood-gates. The water is broken up into foam
on passing through the gates, so that it is quite natural that (6)
should contain less emanation than (4) or (5).
There is not enough radium in a litre of water to grow
sufficient emanation to give a readable leak. Therefore in order
to test for the actual radium-content of the water larger quantities
of water were taken. Two large clean tin cans were filled with
nine litres of Cam water and tap water respectively. The water
was then boiled, the dissolved emanation cleared out, the cans
corked up and the water allowed to rest. After an interval of
some days the water was boiled again and the emanation given
off collected and tested. From the amount accumulated in the
given period the amount accumulated in the first 24 hours was
calculated*.
The results are given in Table II together with some results
obtained with hydrochloric and sulphuric acids.
TABLE II.
Accumulation | Accumulation
Period of rest of emanation | of emanation
in this period | per day per litre
9 litres tap water 6 days ff 02 -
bP) 39 3) 12 bb) 1-2 "02
9 litres Cam water 5 days 1:3 04
bb) 39 bb) 13 bP) 2°3 04
200 c.c. HCl + 300/| since manufacture 1:2
c.c. distilled eve 13 days 15 14
200 c.c. H,SO,+ 400 | since manufacture 0
c.c. distilled water
To express the radium-content of the water in terms of gms.
of radium it was now necessary to use radium solutions of known
strength. A radium solution containing 1:57 x 10~ gm. radium
was kindly presented to the author by Professor Rutherford. This
was divided into two parts, one containing 2ths and the other
3ths and placed in two bottles. Each of these parts was treated
in a manner similar to the above. Instead however of boiling
the solutions, which was impossible as the solutions were in bottles,
the bottles were heated in a bath of boiling brine (b.p. = 105° C.).
The results are given in Table III.
* Suitable tables for this work are given by Kolowrat. Le Radium, 1909.
Mr Satterly, Radiwm-content of Cambridge Waters. 543
TABLE III.
Growth of emanation
Period Mean growth
Radium solution | of rest, of emanation
hours in this per 24 per
period hours 24 hours
204 Gl 8:2
2 : = 742 19°8 76
a Oa hepa crag i ai 8-0
gm. of radium 241 8-4 8-3
473 eet 76
; 233 11:4 ILS
3 : -9 4
Pen Cee a ibe ans
on 233 11:8 11:9
From Table III it follows that 1:57 x 10- gm. radium ac-
cumulates emanation at the rate of approximately 20:0 per day.
From this and Table II it follows that
1 litre tap water contains 1°6 x 10-” gm. radium
1 ” Cam 2) o) 3°2 x LOY ? 3)
1, hydrochloric acid e hee squlblies2 a x
It may also be calculated that the emanation given off by the
initial boiling of one litre of tap water is that which would be in
equilibrium with 130 x 10~? gm. radium, and of one litre of Cam
water that which would be in equilibrium with 5:0 x 10-” gm.
radium.
For the water of the St Lawrence, as already stated, Eve* finds
a radium-content of -25 x 10-” gm. radium per litre, but he does
not state whether this result is obtained from the initial or sub-
sequent boiling. It follows, in either case, that the waters in the
neighbourhood of Cambridge contain a much greater quantity of
radium per unit volume than the waters in the neighbourhood of
Montreal. Naturally therefore the air at Cambridge would contain
a greater quantity of radium emanation than the air at Montreal.
The proportion actually found+ was 10: 6.
It may be mentioned in conclusion that the Cam takes water
which has drained through the Chalk deposits in the south of
Cambridgeshire, and then runs over the clayey deposits at the
base of the Chalk, while the water supply of Cambridge is taken
from springs issuing at Cherryhinton and Fulbourn from the
greensand which hes above the Gault and below the Chalk.
* Phil. Mag. July 1909. + ibid. Oct. 1908, July 1910.
544, Mr Satterly, Radium-content of Charcoal.
Radium-content of some varieties of charcoal.
In my experiments* on the absorption of radium emanation
from the air I have had occasion to measure the rate at which
radium emanation is generated by the charcoal after the charcoal
has been heated to a bright red heat and all its previous store
cleared out. From these results, with the knowledge of the
amount of emanation produced by a known mass of radium in
a known time, it is possible to calculate the radium-content of
the charcoal.
The results are given in Table IV.
TABLE LV.
| Mass Kmanation Mass of Mass of radium
Charcoal of charcoal | accumulated radium in per gram of
tested per day the charcoal charcoal
Coconut 40 rani 1-6 x 10“ gm.) 34 10g om:
. 140 Bt 4x10-",, | 3x108 |
Brazil nut 30 79) AS VOF 2 eee mere
Wood 15 05 MINI, | Si 1
For purposes of comparison with the figures in the last column
it may be mentioned that the average radium-content of rock and
soil is 1-4 x 10-" gm. per gm., and that wood charcoal contains
1—5°/, of ash.
I wish to express my best thanks to Prof. Sir J. J. Thomson
for his kindly interest in these experiments.
* Phil. Mag. Oct. 1908, July 1910.
+ ibid. Oct. 1908, p. 597.
+ ibid. July 1910, p. 7. |
Prof. Pope, Compensated Bases and Dihydropapaverine. 545
The Resolution of Externally Compensated Bases into their
Optically active components. By Professor PopE and Mr J. Reap.
[Read 23 May 1910. ]
The authors show that. when the resolution of an externally
compensated acid (or base) is attempted by crystallisation with an
optically active base (or acid), one of three different kinds of
behaviour is to be observed. (1) The two salts, d-B, d-A, and
d-B, l-A, which are capable of formation, are readily separable by
crystallisation and show no tendency to form solid solutions one
in the other; in this case an easy separation is effected by the
method of Pope and Peachey. (2) The two salts, d-B, d-A and
d-B, l-A, combine to form a partially racemic compound; in this
case no resolution occurs. (3) The two salts, d-B, d-A, and d-B,
l-A, form solid solutions one in the other, and separation by frac-
tional crystallisation is slow and very incomplete.
Behaviour of the type (8) has not been previously distinguished
and a number of cases of its occurrence were described.
The Resolution of Dihydropapaverine. ‘By Professor POPE
and Mr C. S. GIpBSson. .
[Read 23 May 1910.]
The resolution of externally compensated dihydropapaverine
into its optically active components was effected by Pope and
Peachey by crystallisation with d-a-bromocamphor-7-sulphonic
acid; the less soluble salt, /-B, d-A, is crystalline and may be
separated from the salt, d-B, d-A, which is resinous, by fractional
crystallisation. It is now shown that the resolution is more
easily effected by dissolving the externally compensated base in
an equivalent proportion of d8-camphorsulphonic acid and adding
to the aqueous solution one-half an equivalent of ammonium
da-bromocamphor-7-sulphonate; after separating the crystalline
salt of the laevo-component of the alkaloid which is deposited
the purification of the residual dextro-base is effected by crystalli-
sation of its /q-bromocamphor-7r-sulphonate.
546 Dr Sell, Chlorination of a-Picoline.
Further study of the Products of Chlorination of a-Picoline.
By Dr SELL.
[ Read 23 May 1910.]
-One of the most important compounds obtained by the
Cl
or” “ol
| . This
H \ CAs
chlorination of a-picoline has the formula
substance has been shown to produce by the action of sulphuric
acid besides 3. 4. 5. trichloropicolinic acid and 3. 4. 5. trichlo-
ropyridine formerly described, a small quantity of an acid
regarded as 3 oxy 4. 5. dichloropicolinic acid. This compound
is resolved by heat into the corresponding oxydichloropyridine.
The above hexachloropicoline also reacts with alcoholic sodium
hydroxide and yields 4 oxy 3. 5. dichloropicolinic acid, resolved by
heat into 4 oxy 3. 5. dichloropyridine isomeric with the last-
mentioned oxydichloropyridine.
It is also found that 3. 4. 5. trichloropicolinic acid gives with
ammonia 4 amino 3. 5. dichloropicolinic acid which by heat is
resolved into 4 amino 3. 5. dichloropyridine, and the same com-
pound is also formed from 3. 4. 5. trichloropyridine by heating
with ammonia. Finally when the amino group in 4 amino 3. 5.
dichloropyridine is replaced by the hydroxyl group the same
oxydichloropyridine is obtained as was shown to be produced by
alcoholic sodium hydroxide on the original hexachloropicoline and
heating the oxydichloropicolinic acid thus produced.
Messrs Fenton and Wilks, Formation of uric acid derivatives. 547
Formation of uric acid derivatives. By Dr FENTON and
W. A. R. Winks, B.A., Gonville and Caius College.
[Read 23 May, 1910.]
The condensation of urea with dihydroxymaleic acid, or its
derivatives, would appear likely to be of interest from a physio-
logical standpoint owing to the peculiar manner in which this
acid is produced by oxidation in presence of traces of iron. The
authors are making a study of these condensation-products and it
has already been shown that: the acid itself condenses with urea
to give zsovminazalone and, probably, the aldehyde of hydantoic
acid. When the acid is gently oxidised, mesoxalic semi-aldehyde
is obtained; this might be expected to yield uric acid by action of
urea but, under the conditions employed, the result is glycoluril,
a substance closely related to allantoin. By oxidising the acid
with bromine, dihydroxytartaric acid is obtained; this when acted
upon by urea in presence of acetic anhydride is found to yield
a product which appears to be identical with acetyl dialuric acid,
recently obtained by Behrend and Friedrich from dialuric acid
itself. [Annalen 1906 (344) 1.] It gives a violet precipitate
with baryta water and, when evaporated with nitric acid, an intense —
murexide reaction. According to Ascoli and Izar [Zeit. Physiol.
Chem. 1909 (62) 347], dialuric acid and urea under the influence
of liver extract can give rise to uric acid, and it would therefore
appear that the synthesis of the uric acid might be effected from
dihydroxytartaric and urea by the changes indicated. In alcoholic
solution, dihydroxytartaric acid and urea yield the crystalline
salt C,H,O,. 2CO(NH.).; when this is heated to about 100° it
breaks up, probably quantitatively, into carbon dioxide, urea and
hydantown.
The fate of uric acid in the dog. By Harotp Ackroyp, M.B.
(Communicated by Mr W. E. Iixon.)
[Read 6 June, 1910. |
The liver of dogs when perfused with normal saline solution
produces a small quantity of allantom. When sodium urate is
added to the perfusion fluid, a part of the sodium urate is
destroyed: part of this can be recovered as allantoin but not the
whole. No urea could be isolated from such a perfusion fluid.
The liver of a dog has not the power to destroy allantoin.
VOL XV. PL. VI, 36
548 Mr Robinson, The Adsorption
The Adsorption of Acids by Carbohydrates. By F. Ropinson,
B.A. (Communicated by Dr Fenton.)
[Read 23 May, 1910. ]
The action of acids, especially hydrogen chloride and hydrogen
bromide, on carbohydrates has been studied by many chemists
and it now appeared desirable to investigate the nature of the
reaction of the various carbohydrates with the above-mentioned
acids, in order to determine whether the initial phenomenon was
one of adsorption, or chemical action, or both, and if possible to
devise a method of characterising the various carbohydrates with
reference to the capacity of each for absorbing the acid in
question.
In 1809, Bouillon-Lagrange and Vogel (Ann. de Chim. 70, p. 91)
showed that cane sugar, when boiled with aqueous hydrogen
chloride, became coloured and that only a small percentage of the
acid remained combined.
Similar experiments were conducted by Vogel (Ann. de Cham.
82, p. 158) with starch, milk-sugar and hydrogen chloride, but the
product did not contain acid in combination.
Afterwards, Emil Fischer investigated the action of hydrogen
chloride at low temperatures on various sugars, and isolated the
substances known as ‘chlorhydroses.’
In 1898, Fenton and Gostling (Journ. Chem. Society, 1898,
p. 554) observed that levulose with ether and dry hydrogen
bromide almost immediately gave an intense purple colour: further
investigation showed that the ether had nothing to do with the
formation of the colour, since the dry solid absorbed the gas to
give the same purple colour. This reaction, with ether and hydro-
gen bromide, was repeated with various carbobydrates, which were
found to fall into four distinct groups.
(a) With ketohexoses, such as fructose, sorbose, a purple
colour appeared after a few minutes and became very intense in
about one hour: and substances which, by hydrolysis, are capable
of giving rise to these compounds [cane sugar, inulin] gave a
similar effect but rather more slowly, the maximum intensity of
colour being attained in about two hours.
(6) Hexaldoses (dextrose, galactose) and substances capable of
giving rise to them (maltose, lactose, dextrin) showed in the first
instance various shades of yellow, brown, or red and it was only
after long standing that the purple colour was apparent.
The colour never approached that of the first group either in
brilliance or intensity.
of Acids by Carbohydrates. 549
(c) Carbohydrates, whose molecules contain less than six
atoms of carbon (arabinose, glycollic aldehyde) gave brown or red
colours without any appearance of purple, and the polyhydric
alcohols showed only a yellow colour.
(d) Carbohydrates like cellulose and starch gave a very faint
red, or no colouration at all.
In a later communication (J. C. S. Trans. 1899, p. 423), the
same authors showed that the product of the action of hydrogen
bromide on the various carbohydrates was a colourless, crystalline
substance, bromomethylfurfuraldehyde.
The action of hydrogen chloride was found by them to be
similar to that of hydrogen bromide, but the reaction was much
less violent, and the yield of chloromethylfurfuraldehyde not
nearly so good.
Subsequent experiments shewed that all ketoses, or sub-
stances which give rise to these on hydrolysis, yield bromo or
chloromethylfurfuraldehyde under this treatment; the aldoses
give mere traces whereas the ketoses yield from 20—30 per
cent., so that by estimation of the yield a ready method is afforded
of distinguishing the two classes.
Principle of the Method.
A weighed quantity of the various carbohydrates, finely
powdered, was treated with an excess of a standard solution of
dry hydrogen chloride gas in dry chloroform or carbon tetrachloride,
and the mixture was allowed to remain for some hours in tightly
stoppered bottles, at a constant temperature.
The clear liquid was decanted from the solid, a known volume
shaken with much water and titrated against standard baryta,
phenolphthalein being used as indicator.
From this experiment the weight of hydrogen chloride adsorbed
by the solid in each case was easily deduced. »
It was found advisable to cover the solid with a known amount
of pure solvent (generally 5 c.c.), in order to allow the former to
absorb the maximum amount of liquid before the addition of the
standard acid solution.
Experimental.
Experiment I.
Weight of each carbohydrate used, 0°25 gm.
Time of experiment, 18 hours.
Mean temperature, 14°C,
36—2
550 Mr Robinson, The Adsorption
Volume of solution of hydrogen chloride in carbon tetra-
chloride added, 25 c.c.
Strength of solution. 1 cc. contains 000376 gm. of hydro-
gen chloride.
Weight of acid added, 0:0940 gm.
State of ‘ Weight of acid adsorbed
Carbohydrate | solid after Ween
Expemmienk by 0-25 gm. by 100 gms.
Starches. Colourless} 0:0363 gm. | 0:0577 gm. 23-08 gms.
Raftinose ...) Black 0:0384 _,, 00556 ,, 22:24 ,,
Maltose Colourless| 0:0393 ,, 0:0547 ,, DASSiies
Levulose ...| Black 0:0418 ,, 0:052275 20°88 sa,
Cane Sugar| Black 0:0525_ ,, 0:0415 _ ,, 16-60
Cellulose ...| Colourless| 0°0526 ,, 00414 ,, Tor G
Lactose ...|Colourless} 0°0549 ,, 0:0391 ,, 1645 ee
Dextrose ...| Colourless} 0°0565_ ,, 0:0375 ,, 15:00-—;
Experiment II.
Weight of each carbohydrate used, 0°5 gm.
Time of experiment, 21°5 hours.
Mean temperature, 14° C.
Volume of chloroform solution of hydrogen chloride added,
30 c.c.
lec. of solution contained 0:00473 gm. of HCL.
Weight of acid added, 0°1418 gm.
State of 5 Weight of acid adsorbed
Carbohydrate | solid after ee
experiment by 0°5 gm. by 100 gms.
Starch ...... Colourless| 0-0288 gm. | 0:1130gm.| 22-6 gms
Raffinose ...| Black 0:0298 ,, 0:1120 ,, 22-4,
Levulose ...| Black 0:0308 _,, (TAT) se 22°2 =,
Maltose .../Colourless| 0-0368 ,, O050is PAE SB
Cane Sugar| Black 0:0458 ,, 0:0960 _,, LOC ee
Cellulose ...| Colourless| 0-0488 ,, O-09308r IRS Pla he
Dextrose ...}Colourless} 0:0588 ,, 0-:0830_,, 1G Gyan
Lactose ...|Colourless} 0-0658 _,, 0:0760 ,, loa.
of Acids by Carbohydrates. 551
Kaperiment ITI.
Weight of each carbohydrate, 0°25 gm.
Time of experiment, 18 hours.
Mean temperature, 14° C.
Volume of standard solution added to each, 182 c.c.
Volume of solvent (CCI,), 11°8 c.c.
lc.c. of standard solution contained 0:00501 gm.
Weight of hydrogen chloride added, 0:0912 gm.
State of F Weight of acid adsorbed
Carbohydrate | solid after We ern SE
experiment by 0:25 gm. by 100 gms.
Starch ...... Colourless} 0°0317 gm. | 00595 gm. 23°80 gms.
Fructose ...| Black | 00324 , | 0-0588 ,, 23°52,
Raffinose ...| Black | 0-0339 ,, | 0-0573 ,, 29:92 |
Weabimese |Vellowish| 0-0346 . | 0-0566 , 22-64 ,,
Maltose ...|Colourless}| 0-0426 ,, 00486 _,, 19°44 _,,
Cane Sugar| Black | 0-0456 ,, | 0-0456 ,, 18:24 ,,
Dextrose ...;Colourless| 0°0478 _,, 0:0434 ,, ied Ores.
Cellulose ...|Colourless}| 0-°0495 _,, O04 ie 16°68 _,,
Lactose Colourless| 0:0536_,, 0:0376 ,, 15:04 _ ,,
Experiments were now made in order to discover the relation-
ship existing between the amount of acid adsorbed by the solid
and the amount of acid remaining in solution.
For this purpose, one gram of starch was placed in each of
seven tightly stoppered vessels, 10 ¢.c. of dry carbon tetrachloride
were added to each, and the mixture was allowed to stand for
about one hour, so that the starch might become fully saturated
with solvent: various quantities of a solution of hydrogen chloride
in the same solvent were added to each respectively, and the volume
was made up to 100 c.c. with dry solvent.
After remaining at the ordinary temperature for eighteen
hours, 25 c.c. of the clear liquid were withdrawn, shaken about with
much water and the whole was titrated against baryta of known
strength.
From these results, the amount of acid adsorbed by the starch,
and hence the amount left in solution, was determined.
The results are given in detail below.
For purposes of calculation the well-known exponential for-
mula has been used, namely
% _ he,”
a ke,”,
where n and &k are constants.
552 Mr Robinson, The Adsorption
¢ is the amount of acid adsorbed and a is the weight in
grams of the adsorbing substance, therefore a= amount adsorbed
per gm.
C, 1s the final concentration of the solution.
Using any two corresponding values for c, and ¢,, dividing one
equation by the other and taking logarithms, the following ex-
pression is obtained,
log ¢, — log oe,’ = n [log c, — log ¢,'].
_ loge — loge!
Hence n= =.
log ¢, — log ¢,
Starch.
No. of | Volume of Volume of Weight of Weight of Weight of
experi- | HCl solution | dry solvent acid acid aci
ment added added added left used
C.c. C.c. gm. gm. gm.
H 90 10 0:4690 0:1850 0:2840
B 80 20 0-4147 0:1377 0:2770
C 70 30 0:3610 0:1475 0:2135
D 60 40 0:3080 0:1075 0:2005
K 50 50 0:2555 0-0770 0-1785
F 40 60 0°2044 0:0531 0-1513
G 25 75 0:1265 0-0176 0°1089
In experiments H, B, C the starch presented a pink colour
after 18 hours, whereas in the others it remained colourless.
If, in this equation for n, c,’ and c,’, the respective values of the
weight of acid used and the weight of acid left in experiment G,
be regarded as fixed and the corresponding values of ¢, and c¢, in
the other experiments respectively be substituted, the following
values for’n are obtained:
0-41, 045, 032, 035, 034, 0°30.
Mean value 0°36.
On substituting this mean value of n in the original equation,
the following values are obtained for k:
VAT (PES DPB OLE ORG PRA, APEhS
Mean = 2°48. |
of Acids by Carbohydrates. 553
If the corresponding values of log? and nlog c,+logk be
plotted against each other, the curve obtained is approximately a
straight line.
These concentration experiments were repeated with cane
sugar, a carbohydrate which blackens in contact with the acid
and which gives fairly large quantities of chloromethylfurfural-
dehyde when heated with hydrogen chloride under pressure.
One gram of finely-powdered cane sugar was treated with a
known quantity of pure solvent, then with various quantities of
a standard solution of the acid in dry carbon tetrachloride and the
volume was made up to 80 c.c. with dry solvent.
The mixture was left at the temperature of the room for
18 hours and the amount of acid remaining in solution was
determined as before.
lc.c. of solution contained 0:0026 gm. of hydrogen chloride.
Cane Sugar.
No. of State of Volume of | Volume of | Weight of | Weight of | Weight of
experi-| solid after | solution | solvent HCl acid acid
ment | experiment added added added used left
c.c. C.c. em. em. em.
J Blackened 70 10 0-182 0:0613 | 0:1207
E rE 60 20 0-156 0:0606 | 0:0954
D less ,, 50 30 0-130 0-0533 | 0:0767
C less ,, 40 40 0-104 0:0431 0:0609
G Colourless 10 70 0-026 0:0164 | 0:0095
Here again the exponential formula was used and n determined
by substituting the values of ¢, and c¢, in the expression
_ log ¢, — log ¢/
~ log ¢ — log ¢,’’
where ¢,, ¢,/ &c. are the various values of ¢,; c, ¢c, &c. are the
corresponding values of ¢,.
If n be calculated.as before, the following results are obtained:
0525.0 ai OSG, 10:52:
Mean = 0°54.
Mr Robinson, The Adsorption
The corresponding values for & are
205-5230. SRA 0S. Base
Mean = 2°19.
If the values of log 2 and logk’+nlog ce, be respectively plotted,
the resulting curve is approximately a straight line.
Experiments with Hydrogen Bromide.
Experiment I.
Weight of carbohydrate in each case, 0°5 gm.
Mean temperature, 155° C.
Time of experiment, 19°5 hours.
Volume of solution of acid in chloroform added, 25 ec.c.
Strength of solution, 0°00758 gm. of acid per c.c.
Weight of acid added, 0°1895 gm.
State of Weicht of Weight of Weight of
Carbohydrate | solid after so acid acid adsorbed
experiment acidilert adsorbed per gram
Rathnose.... Blackened | 0:0077 gm. | 071818 gm. | 0°3636 gm.
Levulose | Blackened | 0:0100_,, 01795 ,, 0:3590 ,,
Starch..... || clourless}{ 0116 ,, | O1779 ,, | 08558,
colourless } ,
Cane Sugar) Blackened | 0-0200 ,, 0:1695 ,, 0°3390 ,,
Maltose ... Pink 0:0247 ,, 01648 ,, 0:3296 ,,
Cellulose...) Yellow 00403 _,, 0:1492 ,, 0:2984 ,,
Lactose Yellow 0:0668 ,, O1230 02454 ,,
Dextrose... Pink 0-:0681 ,, 0:1214 ,, 0:2428 ,,
Hydrogen Bromide.
Experiment II.
Weight of carbohydrate used, 0°5 gm.
Temperature, 17° C.
Time of experiment, 18°5 hours.
Volume of solution of acid in chloroform added, 30 c.c.
Strength of solution, 0°00652 gm. per c.c.
Weight of acid added, 01986 om.
of Acids by Carbohydrates. 555
: Weight of Weight of
Carbohydrate aera dea acid A AeorbOR
adsorbed per gram
UAC, phrcazo eee 0:0096 gm. | 01890 gm. | 0-3780 gm,
Levulose: ....es05265 00212 ,, Oi ita. 0°3548 _,,
PyALMOSC c 42222424447 00231 “,; O-Tiaa O-3510. 1.
Cane Sugar ......... 0-0328--,, 0:1658 ,, 03316,
Maltose o...2220.00 0:0463 _,, 0°1523 ,, 0:3046 ,,
CEVMOSE .... icone. o>: 0-0723 ,, 0-1258 ,, 0-2516 ,,
Dextrose :.. 5.22... 00791. |, OAS. ., 0-2390 ,,
NE ACHOSO! oi riindiesobe oot 071044 ,, 00942 ,, 0:1884 ,,
Hydrogen Bromide. Experiment III.
Weight of carbohydrate, 0°5 gm.
Temperature, 17° C.
Time of experiment, 18°5 hours.
Volume of solution of acid in chloroform added, 30 c.c.
Strength of solution, 000613 gm. per cc.
Weight of acid added, 0°1839 gm.
; Weight of Weight of
Carbohydrate eee acd acid zileetlied
adsorbed per gram
SUBIC Ce eee 00154 gm. | 0:1685 gm. | 0°3370 gm.
WevWlose: 22... 0+ 22.5. 0-01 ai 0:1646 ,, OB292. 5
Rathnose +2052. 0.033 00232" ,, ONGOM, oa MOrB21Ay
Cane Sugar ......... 00366) OA 02946 ;,
Maltose: i5...6.6.... 00405 _,, O-T434 |, 0°2868 ,,
CEUINOSS, 2 2b copies 0-0707_,, 0°1132. ,, 02264 ,,
DDERbLOSE oo fcaree 0:0838 _,, OA0OT 0:2002 ,,
WACTOSE.. hes. adeas 0:0870_,, 00969: |,, 0°1938_ ,,
Concentration experiments with Hydrogen Bromide.
One gram of cellulose, dried for several hours at 100° C., was
weighed into each of five stoppered vessels, 10 c.c. of dry carbon
tetrachloride were added to each and the mixture was allowed to
stand for some time so that the cellulose might become fully
saturated with solvent: various quantities of a solution of hydrogen
bromide in the same solvent were added to each respectively and
the volume was made up to 70 c.c. with dry solvent.
After standing for eighteen hours, at the ordinary temperature,
556 Mr Robinson, The Adsorption
25 c.c. of the clear liquid were withdrawn, shaken about with much
water and the whole was titrated against baryta of known strength,
phenolphthalein being used as indicator.
In each experiment, the cellulose became darker in colour, the
stronger solutions of the acid producing the deepest colour.
Strength of solution, 1 ¢.c. contains ‘01161 gm. of HBr.
Cellulose and Hydrogen Bromide.
No. of | Volume of Volume of Weight of Weight of Weight of
experi- solvent solution acid acid acid
ment added added added used left
c.c. C.c. gm. em. gm.
F 50 20 0:2322 0:1820 0-:0502
G 40 30 0-3482 0:2407 0:1075
H 30 40 0:4644 0:2888 0-1756
ih 20 50 05804 0:3028 Oia
J 10 60 0:6966 03328 0-3638
The exponential formula was again employed and the following
values were obtained for n:
0:37, 0°37, 0:30, 0°30.
Mean = 0°33.
The corresponding values for & are
1:98, 2:04, 2:08, 1:88, 1°89.
Mean = 1:97.
If the corresponding values of log @ and logk+nlog ec, be
plotted against each other, the following results are obtained.
= is the weight of acid adsorbed per gram of cellulose, ¢, is
the final concentration of the solution.
log c, log k +n log c,
— 0-740 — 0:748
— 0:618 — 0°634
— 0-539 — 0:565
— 0°519 — 0-498
— 0:478 — 0-459
of Acids by Carbohydrates. 557
AP
Se pert
ee
“an a
Concentration experiments were made with hydrogen bromide
and cane sugar, a carbohydrate which readily blackens with this
acid, and the following results obtained:
Weight of sugar, 1:0 gm.
Concentration of acid added, 0:01434 gm. HBr. per c.c.
Temperature 17°C.
Time, 18°5 hours.
No. of | Volume of | Volume of | Weight of Weight of Weight of
experi- solvent solution acid acid acid
ment added added added left used
C.C. c.c. gm. gm. gm.
B 60 10 0:1434 0:0322 01112
G 50 20 0:2868 0:0785 0:2083
E 20 50 0:7170 0:2856 04314
D 10 60 0:8604 0°3605 0:5000
I 0 70 1:0038 0:4320 0:5718
558 Mr Robinson, The Adsorption of Acids by Carbohydrates,
In every case the solid was completely blackened, and with
the stronger solutions the colour of the solution became yellow.
nm was calculated in the same way as before with the following
results:
0:70, 062, 062, 0°63.
Mean = 0°64.
The corresponding values for & are
153, 161, 146, 146, 14:8.
Mean = 15:0.
Summary of results.
(1) Carbohydrates adsorb hydrogen chloride and hydrogen
bromide with great readiness at the ordinary temperature, but
the quantity of acid adsorbed varies greatly with the carbohydrate
considered.
(2) The relative order of adsorption seems to show no relation-
ship to the chemical constitution and properties of the various
carbohydrates and hence no method has been obtained for cha-
racterising them.
There appears to be no definite connexion between the ad-
sorbing power for these acids and the production of bromo or
chloromethylfurfuraldehyde, since starch gives an extremely minute
yield of bromomethylfurfuraldehyde, yet it adsorbs most acid.
The hexaldoses always appear at the bottom of the table.
Maltose and lactose differ widely in their powers of adsorption,
although they bear a great resemblance in their chemical
properties.
(3) The initial phenomenon agrees with that generally ac-
cepted for adsorption, and constant values for n and k have been
determined by experiment.
(4) The process probably consists of a rapid condensation of
the acid on the surface of the solid and afterwards it works its way
into the interior: this is evidenced by fructose and sucrose and
hydrogen bromide, in which case the sugar first becomes pink and
eventually black: this black colour may be either due to chemical
action or to the formation of an ‘adsorption compound’ as in the
case of the so-called ‘iodide of starch.’
In conclusion, J wish to tender my best thanks to Dr Fenton
for suggesting this research, and for much kind help received
during its progress.
Prof. Woodhead, The results of Sterilisation, etc. 559
The results of Sterilsation Haperiments on the Cambridge
Water. By G. Situs WoopuHeaD, M.A., Trinity Hall, Professor
of Pathology.
[Received 20 July 1910.]
Although the sterilisation of water has a special local interest
at the present time, it is bound to come into greater general
prominence as time goes on and as sources from which pure
drinking water may be obtained become restricted in number,
and as the collecting grounds for the present supplies are built
over and sewers are carried through them. Without entering
into any discussion as to the bacteriological purity of the Cam-
bridge water, a question on which, however, I hold a very strong
opinion, I may point out that in the interests of both consumers
and water company, in view of the report of the Local Govern-
ment Board* on the “potential danger” of contamination, it was
necessary to adopt some method of eliminating any such potential
danger by adapting or devising a method of sterilising the water
or, failing this, of having recourse to a new supply.
Of the methods that have, from time to time, been suggested,
some five or six in number, one was soon proved to be unsatis-
factory—Clark’s method of softening and sedimentation.
Another, sand filtration, was also set down as unsatisfactory
and for the following reasons. The Cambridge water, beautifully
clear and bright, contains a very small amount of organic matter,
so little, indeed, that the formation of an organic filtering film
can go on very slowly and, as is now fully recognised, until such
film is formed on its surface no sand filter is reliable, that is, it
will not keep back the necessary proportion of microorganisms.
Experience has proved that filtration of chalk water,—unless such
water contains a fair amount of organic matter in suspension and
in solution, or argillaceous material in suspension,—is practically
useless.
A third method, sterilisation by heat, though no doubt effica-
cious, appeared to involve too great expense and too large an
amount of apparatus to be entirely satisfactory. No doubt satis-
factory results could be obtained but it is impossible to test this
method without a very large preliminary outlay, an outlay which,
if the method were unsatisfactory or too costly to run, would of
course be entirely lost.
* Thomson and Crosthwaite, Report to the Local Government Board on
Cambridge Water Supply, London, 1908.
560 Prof. Woodhead, The results of
Another suggestion was that sterilisation by ultra-violet rays
might be adopted, especially as the Cambridge water, beautifully
clear, would allow of the ready passage of these rays through its
substance. On making enquiries, however, we could then hear of
only one small apparatus, an apparatus capable of sterilising some
132 gallons only per hour of an ordinary water supply, more or
less according to the translucency of the water. The apparatus a
Cooper-Hewitt lamp made from transparent quartz requires for
its proper working 3 amperes of current at 110 volts. With this
the process of sterilisation had been carried on on a purely experi-
mental scale and the apparatus required would be somewhat costly
as it had been determined by the Water Company that any
sterilisation experiments carried out on their behalf must be on
a sufficiently large scale to supply sterilised water in sufficient
quantities for, say, a couple of thousand people.
Ozonisation of the water, the next method that was suggested,
has passed somewhat beyond the experimental stage, but although
ozonising installations for the sterilisation of water could be seen
in various towns in France and Germany there were none to which
we could gain access in this country. On making enquiries it was
found that the water supplied to Paris is very like the Cambridge
water in its chemical composition. We were told that it had
been selected specially because of its high degree of hardness, the
Commission appointed to find a water supply for Paris main-
taining that the use of a hard water is attended with fewer
dangers to the human subject than when a soft water is used.
The Commission evidently had in view, in this connection, rickets,
imperfect bone formation and lead poisoning. At the request of
the Water Company Mr Heycock and I journeyed to Paris where
we found that the pure chalk water becomes somewhat muddied
and otherwise contaminated on its passage from its source by the
Marne river to the intake of the Paris Water Company at St Maur
where it contains a very large number of the Bacillus colt com-
munis. In order to get rid of a large proportion of these organisms
and to remove the organic matter, the presence of both of which
would interfere greatly with the process of sterilisation by ozone,
the water at St Maur is passed through sand-filters, by means of
which process a certain degree of clarity—almost equal to that
of the Cambridge water—the removal of a considerable quantity
of organic matter and the reduction of the number of the Baczllus
coli to such a point that, usually, not more than one Bacillus cola
to 40 c.c. of water is obtained. As a matter of actual experience,
however, at the time we visited St Maur, these filters were not
working quite up to this standard, for although the whole of the
organic matter, except some of that in solution and the whole of
the inorganic matter in suspension was removed the water then
s
Sterilisation Experiments on the Cambridge Water. 561
becoming clear and bright, the reduction in the number of the
Bacillus coli was not up to the standard given above, a single
organism being found sometimes in 10 c.c., sometimes in 20 c.c.
and sometimes in 30c.c. For all practical purposes, however, this
was sufficient, for, on examining bacterioscopically the water that
had been treated in a de Frise tower by ozone produced in a
Siemens-Halske generating apparatus*, 500 c.c. contained not a
single Bacillus coli. It is evident then that in ozonisation we
have a sterilising method which, applied to the Cambridge water,
will probably give excellent results. In order to obtain complete
sterilisation a low amount of organic matter and a small number
of organisms seemed to be essential as, on adding organic matter
and increasing the amount of Bacillus coli the quantity of ozone
required to bring about sterilisation seemed to increase out of all
proportion to the amount of these substances added. In con-
nection with this it should be remembered that when we speak
of sterilisation of water we refer to the destruction of disease-
producing germs or of organisms that are usually found alongside
such disease-producing germs. Sporebearing organisms need not,
here, be taken into account, as the presence of the sporebearing
organisms usually found in water affords no indication of the
presence of dangerous contamination. Streptococci and the Ba-
cillus coli communis, especially the latter, are the indicators we
search for as affording evidence of a possibly dangerous con-
tamination, whilst any method of sterilisation that will effectually
destroy these may be relied upon to destroy equally, or more,
easily any of the disease-producing organisms such as the typhoid
bacillus or the cholera bacillus that may have gained access to
the water supply.
The Cambridge water is quite clear, contains a very small
quantity of organic matter, and the number of organisms is
exceedingly low, much lower indeed than in the majority of the
water supplies in the United Kingdom; it is therefore an excel-
lent water on which to try the various processes of sterilisation.
From the sentimental point of view there seemed to be no
objection to the treatment of any water by ozone; even those
who object to the addition of chemicals to water would probably
not object to the addition of the “health-giving” ozone. I mention
this at this point because, curiously enough, when we came to
consider the next method we found that certain waters con-
taining organic matter acquired a peculiar taste when treated
with chlorine and at first we supposed that this was something
specially associated with the taste of chlorine. When, however,
- * See de Frise, Stérilisation de Veau par Vozone, 1907; Daske, Deutsche
Vierteljahrzcshr. f. offentl. Geswndheitspflege, Braunschweig, Bd. 41, 1909, for
description,
562 Prof: Woodhead, The results of
we came to treat the same water with ozone we obtained a similar
taste. With neither of these substances, chlorine or ozone, was
this taste obtained in the filtered Paris water or in the unfiltered
Cambridge water, so that we put the taste down to the action of
the chlorine or the ozone upon an excessive amount of organic
matter present. These substances, which appear to be related to
the amines, chloramines, etc. must be further studied*.
The next method of sterilisation suggested was the treatment
of the water with chlorine. In 1894 Dr Cartwright Wood and
I+ were much struck by the remarkable sterilising power of
Hermite’s solution—electrolised sea water containing chlorine
and hypochlorous acid. We found that very minute quantities
of this solution rendered sterile clear sewage from which much of
the organic matter had been removed and that in larger quantities
it was a most powerful disinfectant even in the presence of con-
siderable quantities of organic matter.
In 1897 I had to go into the question of the sterilisation of
the reservoirs and water mains at Maidstone during the great
typhoid epidemic}. Having in view Professor Delepine’s experi-
ments on disinfection by means of “bleach” solution, I filled
the whole of the Maidstone mains from the gravitation reservoir
with a 1—300 solution of chloride of lime or bleaching powder.
From the complaints received by the Water Company from all
sources I was satisfied that we had attained our object.
In 1898 Kanthack, Robinson and Rideal§ carried out a series
of experiments on a similar substance known as “ Electrozone ”
by which “sewage tank effluent” or the filtrate from bacteria
beds was rendered almost germ-free. They found, however, that
the amount of organic matter was not diminished to any very
great extent by this treatment.
In 1903 Lieutenant V. B. Nesfield, I.M.S.||, was so impressed
with the activity of chlorine in its sterilising power in relation to
sewage that he applied it to the sterilisation of water, using one
part of chlorine to 8,000 parts of water. This, of course, was
invariably sufficient to sterilise water, even that to which a con-
siderable quantity of organic matter containing the Bacillus colz
communis had been added. He used a tablet containing one and
a half grains of bleaching powder mixed thoroughly with half a
grain of sodium bicarbonate, this latter being added to keep the
* Tt was found later that some of the taste was due to presence of oil blown over
the ozonizing area along with the air from the air pump. |
+ Lancet, London, 1894, Vol. 1, p. 1321. |
+ Woodhead and Ware, Trans. Soc. Engineers, Session 1900—1901, London, |
1901, p. 49.
§ See Rideal, Sewage and Bacterial Purification of Sewage, London, 1900,
Delos
|| Public Health, July, 1903.
Sterilisation Experiments on the Cambridge Water. 563
tablet dry and to provide, when added to water, the acid radicle
CO necessary to liberate the feebly combined chlorine of the
bleaching powder. Water which may be teeming with typhoid
or colon bacilli becomes sterile within five minutes of the solution
in it of this tablet. He points out further that the addition of
a quarter of a grain of sodium sulphite to the pint of water so
treated is free from chlorine and is practically tasteless.
[Cl], + H,O + Na,SO, = Na,SO,+ 2HCL.]
This method of sterilisation of water has been put into practice
on a considerable scale in India and has been very effective in
preventing the spread of water-borne disease amongst troops on
active service.
The relatively better results obtained in the sterilisation of
water than in the treatment of sewage is accounted for by the
fact that sewage contains such a relatively large amount of
organic matter and so many spore-bearing organisms. Pathogenic
water-borne organisms, however, are killed by chlorine with very
great readiness even in sewage, the “filter effluents” of the Boston
sewage, as pointed out by Professor E. B. Phelps*, being almost
sterilised by 3°5 parts per million, 99:2°/, of the coli organisms
succumbing within two hours, whilst 2°2 parts of available chlorine
per million is sufficient to act im the same way on the Baltimore
filter effluent—a somewhat weaker effluent. Although complete
sterilisation required a considerably larger amount of chlorine
there are here indications of the ease with which sterilisation
may be carried on in the presence of even large quantities of
organic matter; water containing a small quantity of organic
matter is of course more readily sterilised.
In 1905 Houston and McGowanf sterilised with chlorine the
whole of the Lincoln water supplying a population of about 50,000.
In the first instance they used one part of Chloros in 10,000 parts
of water. As Chloros contains 10°/, of available chlorine they
were using 10 parts chlorine per 1,000,000 of water. Later only
five parts per 1,000,000 and ultimately one part per 1,000,000 was
used. In this case, however, the sterilisation was not complete
though the number of Bacillus coli communis found in the treated
water was undoubtedly small. They found that after treatment
77°3°/, of the 163 samples contained no Bacillus coli in 100 c.c.,
and that 17-7 °/, contained Bacillus coli in 100 c.c. but not in 1 c.c.
Drs Houston and McGowan were of course dealing with a river
water and surface water from land drains of an agricultural
country and from a series of old sandpits containing a consider-
* The Disinfection of Sewage and Sewage Filter Efflucnts, Washington, 1909.
+ Supplement to 35th Annual Report of Local Government Board for 1905-6,
London, 1908.
VOL. XV. PT. VI. af
564 Prof. Woodhead, The results of
able quantity of organic matter and a large number of micro-
organisms; the results obtained must therefore be looked upon
as exceedingly satisfactory.
Then came Dr Phelps’ experiments followed by Dr Thresh’s
paper in the Lancet*. The latter, beginning where Dr Houston
had left off, showed that one part of chlorine in a million of water
was fatal to the Bacillus coli in 24 minutes. He followed this up
with a series of experiments in which he found that 0°75 parts in
1,000,000 of water was still effective as a sterilising agent. Thresh
suggested, too, that any chlorine not taken up by the micro-
organisms or other organic matter present in the water should
be neutralised by the addition of bisulphite of soda.
Repeating these experiments but using Cambridge water
I found that all that was claimed for this method was under-
rather than over-stated, and that the limit at which chlorine
would act as a sterilising agent had not yet been reached, and
after carrying out a number of laboratory experiments I came to
the conclusion that here we had the key to the solution of the
question of the sterilisation of the Cambridge water. Continuing
I found that “bleach ” solutions containing one part of chlorine in
two millions of water or even one part in four millions of water if
left to act for half an hour upon Baczllus coli added to the water
killed these bacteria. Typhoid bacilli added were similarly de-
stroyed. Again I found that on adding organic matter, such as
broth, to water containing these bacteria it was necessary, in order
to obtain complete sterilisation, to mtroduce a larger amount of
chlorine and that until much of this organic matter was saturated
with chlorine the chlorine did not attack the bacilli. As soon,
however, as a certain degree of saturation was effected the bacilli
were attacked and destroyed by any slight excess of chlorine.
These laboratory experiments were repeated time after time and
in each case with similar results. Continuing the experiments
suggested by Dr Thresh on the use of bisulphite of soda as a
“Chlorine killer” or neutraliser I found that where an excess of
chlorine was used in the presence of non-putrifying organic matter
the process of neutralisation both as regards taste and smell was
effective, but that in the presence of considerable quantities of
decomposing organic matter, although the chemical neutralisation
of the chlorine was effected, a peculiar iodoform taste and smell
remained and it was very difficult to get rid of either taste or
smell by continued storage or by the action of light, heat, ete.
Then it was found that Cambridge water to which chlorime
was added in the proportion of one part to six, seven or eight,
millions of water, though completely sterilised, retained not a trace
* Lancet, London, 1908, Vol. 1. p. 1597.
Sterilisation Haperiments on the Cambridge Water. 565
of either taste or smell of chlorine; in the later experiments
therefore no neutralisation by means of bisulphite was considered
necessary, especially as it was a difficult matter to keep the
bisulphite solution free from organisms which, of course, could
remain alive and active in the neutralised chlorine solution.
It is generally accepted as indicated by Odling that dry
“chloride of lime ”—“ bleaching” powder—on being mixed with
water is split up into calcium chloride and calcium hypochlorite
to the latter of which, in the presence of a weak acid in the water,
the sterilising power of chloride of lime is apparently due. Probably
the best acid for the purpose is carbonic acid, carbon dioxide,
which, releasing the hypochlorous acid from its combination with
the base, does not cause it to break up, at once, at any rate. Thus,
bleaching powder on being dissolved in water is said to break up
into calcium hypochlorite.
Jo
[20ac Pier CaCl, + Ca(Cl0),.]
This latter, in the presence of the dissolved carbon dioxide, be-
comes converted into calcium carbonate and active hypochlorous
acid
[Ca (ClO), + CO, + H,O = CaCO, + 2HC10],
the hypochlorous acid combining with organic matter directly or
breaking up into hydrochloric acid and oxygen which, in a nascent
condition, acting upon micro-organisms as does ozone speedily
deprives them of vitality.
[2HC1O = 2HCl + O,.]
Organic matter, ammonium salts, and even amido-compounds,
according to Rideal are attacked by chlorine at once so that any
excess of organic matter in water militates against effective
sterilisation when small quantities of chlorine are used. Where,
however, the amount of organic matter is small and the amount
of carbon dioxide dissolved in the water is considerable the con-
ditions for sterilisation by chlorine are ideal. Only when the
reduction of the chlorine compounds is complete and they are
converted into hydrochloric acid are the best results obtained, the
largest amount of oxygen possible then being set free in a nascent
condition, and, the hydrochloric acid being tasteless or combining
readily with the earthy basic substances, there is little chance of
either disagreeable odour cr taste being left in the water. In the
presence of ammonia, urea and similar substances, although oxygen
may be set free and the chlorine may combine with the nitro-
genous compound, a certain amount of nitrogen is liberated and
37—2
566 Prof. Woodhead, The results of
a series of disagreeable compounds described as “chloramines”
may be formed, these imparting to the treated water a persistent
and disagreeable taste and smell. Hence in the presence of large
quantities of organic matter especially when decomposing or
capable of rapid decomposition it may be essential that the water
should be submitted to some preliminary treatment. In the case
of the Cambridge water, however, this is certainly unnecessary.
Bearing on this point it may be noted (1) that the amount
of chlorine sufficient to sterilise waters contaming considerable
amounts of organic matter can not be neutralised as regards taste
and smell by the addition of bisulphite of soda; (2) that such
taste and smell may be present even when the process of sterilisa-
tion is not complete and when no free chlorine can be demonstrated
by the iodide of potassium and starch test, whilst on the other
hand water that contains only small quantities of organic matter
may be completely sterilised and a slight violet iodine-starch re-
action indicating the presence of a faint trace of available chlorine
still unused, may still be present without the slightest trace of
either taste or smell of chlorine remaining in the water. If such
water be exposed to light or to a slightly higher temperature this
trace of available chlorine disappears and, in all probability, is
rapidly converted into hydrochloric acid.
The experiments carried out in the laboratory were not of
course on a sufficiently large scale on which to base final con-
clusions as to sterilisation. The Directors of the Cambridge Water
Company and Mr Gray, the Manager, who all along were most
anxious to place full facilities for carrying out these experiments
at my disposal, requested Mr Hawksley to erect a plant with
which the sterilising process might be carried out on a “practical”
scale. This consists of (1) a chlorinating cylinder capable of
holding about 7000 gallons, so that water passing through this
cylinder at the rate of 7000 gallons per hour should remain in
contact with any chlorine solution entering the cylinder along
with the water for about one hour or thereabouts, the time of
contact of course being halved when double the amount of water
is passed through the cylinder*; (2) a series of mixing and settling
tanks, each containing 700 gallons of water. In one of these tanks
is prepared the bleach solution and in another the neutralising or
bisulphite of soda solution, the other tanks are used as settling
tanks, one for each solution; (3) a couple of pumps so regulated
that measured quantities of the bleach solution may be pumped
into the water as it enters the chlorinating cylinder, and of the
bisulphite solution as the water leaves the cylinder. Measured
* Asa matter of fact some of the water passed through the cylinder in about
18 minutes, but most of it remained in the cylinder for nearly an hour.
Sterilisation Haperiments on the Cambridge Water. 567
quantities of chlorine, say from one part in a million of water to
one part in eight millions, may thus be pumped into the water
entering the chlorinating vessel. Here the two are left in contact
as they pass through the cylinder, the chlorine can then, if
necessary, be wholly or partly neutralised by the bisulphite of
soda solution which is thrown into the water as it leaves the
cylinder. The water as it leaves the cylinder flows into (4) a
galvanised iron tank over a slotted weir so graduated that the
amount of water passing over it at any given time may be easily
measured. All samples of the treated water were collected as it
passed over this weir. With this apparatus, capable of treating
84,000 gallons per day of 12 hours, sufficient for a community
of from 2000 to 2500 people or, if running for 24 hours for 5000
people, a series of experiments were made. At first there was
some difficulty in obtaining a steady working of the pumps, then
certain difficulties arose in connection with the sterility of the
bisulphite solution and again with the balancing or neutralising
of the chlorine by the bisulphite owing to the marked instability
of the latter salt which seemed to become oxidised very rapidly
indeed. Ultimately these difficulties were overcome and out of
six experiments made between the 8th December 1909 and the
6th January 1910 samples varying from 110 to 150 c.c. of treated
water collected at the weir were found to contain not a single
Bacillus coli or any of its congeners. In all these experiments one
part of chlorine per million of water was used and, to get rid of
the taste of chlorine, it was always necessary to neutralise by
means of bisulphite of soda. When complete neutralisation was
obtained neither taste nor smell of chlorine remained. The amount
of chlorine was then halved and the amount of water tested for the
presence of coli increased. 300 c.c. of the treated water taken at
the weir contained not a single Bacillus coli or any organism
resembling it. Between the 10th January and the 2nd February
1910 fourteen further experiments were carried out, the amount
of chlorine per million of water being again halved, only one part
of available chlorine being added to four million parts of water.
Here, again, larger quantities of water, in no case less than half
a litre, were tested, and in every instance it was found that the
organisms of the Bacillus coli group had been destroyed. The
method of testing, though simple, was very efficient. A strong
solution of McConkey’s bile salts glucose litmus medium was
prepared and a small quantity placed in a litre flask. This,
plugged with cotton-wool, was thoroughly sterilised and taken
out to the Fulbourn pumping station where the experiments were
carried out. At the weir the cotton-wool plug was removed and
half a litre of the treated water was allowed to flow directly into
the flask; the lip of this flask had, of course, been carefully pro-
568 - Prof. Woodhead, The results of
tected from dust by a cotton-wool plug covered with tough paper
that would stand sterilisation by heat. Sometimes three or four
of these large flasks were used during a single day, whilst smaller
quantities of the treated water—50 and 100 c.c.—were tested in a
similar fashion especially during the earlier experiments ; latterly,
however, when it was found that the sterilising process was so
complete, only the larger quantities were used. ‘These flasks were
then incubated for forty-eight hours; if the Bacillus coli was
present acid was formed, the litmus turning red and gas bubbles
making their appearance at the surface. Where there is any doubt
as to the formation of gas this can readily be determined by
plunging a warm platinum wire into the medium; if there is no gas
no bubbles make their appearance, whilst if gas is being formed
a large number of small bubbles rise to the surface at the margin
of the fluid. This test, known as the “presumptive coli test” is
admirable where it is desired to prove a negative, but by itself it
is not sufficient to indicate the presence of the true Bacvllus coli;
for our purposes, however, it was all that was necessary, and as
we had an enormous number of samples to test we accepted the
absence of acid and gas as a proof of the absence not only of the
true Bacillus colt but of its congeners. Even where the Bacillus
colt had been completely eliminated a few colonies of spore-bearing
organisms sometimes made their appearance on agar- and gelatin-
plates ; these however were present in exceedingly small numbers
and may be disregarded; they are not anthrax bacilli nor are they
Bacillus enteritidis sporogenes, an organism we have never found
in the Cambridge water.
The above experiments seldom extended over more than four
or five hours each and were devoted mainly to getting the ap-
paratus “tuned” and although such comparatively good results
were obtained the experiments during this period were not looked
upon as being either crucial or final. Only on one occasion—
when the pumps were being regulated—was any sample found to
contain a coliform organism in 50 c.c. of treated water.
In order to obtain prolonged tests under actual working con-
ditions a second series of experiments was carried out. This series
extended over 15 days, the pumping engine running from 5.30 a.m.
to 5.30 p.m. each day. During this period half-hourly observations
were taken and on certain days samples were sent to Professor
Frankland, Dr Thresh, Dr Houston and Dr Otto Hehner.. Here
again on the first and second days of this series we were occupied
in regulating the pumps and testing the process of neutralisation
of the chlorine by the bisulphite of soda solution and the results
obtained were somewhat irregular. At certain periods complete
sterilisation of the water was attained whilst at others, especially
when the pumps were being regulated and we had an excess of
Sterilisation Eaperiments on the Cambridge Water. 569
bisulphite of soda with its contaminating organisms, acid and gas
reactions were obtained in 50 c.c. of water, the results obtained
by the other bacteriologists coinciding almost exactly with those
obtained in the Cambridge laboratories; one of them finding
organisms of the coli group in 50 cc. of water, the other three
finding none in 500 cc. of water. On the next three days of the
run every sample of the treated water taken and tested was found
to be free from any of the coliform (or any other non-sporing)
organisms. Alterations had then to be made in the pumps and
in the neutralising solution, and the results were less satisfac-
tory, but the following day “sterilisation” was again com-
plete. Up to this point we had been working with one part of
chlorine in 1,000,000 parts of water. The following day the
strength was altered to one part of chlorine in 2,000,000 parts
of water. The first sample taken after this change was made
was found to contain acid-forming organisms though no gas was
produced in 100 cc. of water. From this point on to the end of
the fourth day of this experiment sterilisation was complete in
every instance, quantities from one to two litres being tested.
The following day the chlorine was reduced to one part in
4,000,000 parts of water. Here again although sterilisation was
complete on almost every occasion that samples were taken,
twice—in one sample taken at twelve o'clock giving a develop-
ment of acid and gas in 100 c.c. of water and a second sample
taken at 5.30 in which acid only was developed—the process
of sterilisation was incomplete. On the two following days com-
plete sterilisation was obtained throughout the whole of the run.
In all these experiments bisulphite of soda solution was used to
neutralise any excess of chlorine and to remove any slight taste
and smell of this substance from the treated water. It will be
noticed that only on the first day on which any single strength
of chlorine was used were any failures to effect complete sterilisa-
tion noted, whilst even on these days a failure occurred only at
certain periods, periods during which, owing to irregularity of
the action of the pump or imperfectly regulated valves, too large
a quantity of bisulphite of soda solution, and with it probably
certain contaminating organisms, was thrown into the chlorinating
vessel. As we gained experience concerning the contamination
of the bisulphite solution, of the working of the pumps, and of
the falling off in strength of the bisulphite solution, irregularities
in the results obtained were gradually eliminated.
Following these experiments the installation was run for a
couple of days so as to introduce one part of chlorine into between
7,000,000 and 8,000,000 parts of water. Here the excess of
chlorine unabsorbed was so slight that neutralisation was un-
necessary as there was neither taste nor smell of chlorine in any
570 Prof. Woodhead, The results of
of the samples of water taken from the weir. Sterilisation, as
regards the coliform organisms, was absolute.
At this time however I was satisfied that we were not ob-
taining the greatest possible amount of work from our chlorinating
cylinder, and that a small proportion of the water was passing
through the cylinder unnecessarily quickly and was therefore in
contact with the chlorine for too short a time. Using per-
manganate of potash in place of chlorine it was found that
a trace of colour made its appearance at the weir in about
18 minutes. In order to prolong the period of contact and to
prevent this somewhat rapid and irregular passage of a portion
of the water a number of simpie baffle plates were inserted. By
these the passage of the water was so far delayed and regularised
that the first trace of an introduced colouring matter made its
appearance in about 20 minutes, so that none of the water could
pass through the cylinder without being in contact with chlorine
for at least that period before it was neutralised; the bulk re-
mained in the cylinder for about an hour.
After these alterations had been made another series of experi-
ments extending over 12 days (12 hours each day) was carried
out. Here again we had a run, first for three days with one part
of chlorine per million parts of water, the chlorine afterwards being
neutralised by a calculated amount of bisulphite of soda. The
results obtained were exceedingly unsatisfactory on the first two
days and, even on the third, the results were not good. On
searching for the cause of this it was found that the bisulphite
solution was not sterile and that the organisms contained in it
were passing into the water taken at the weir. The chlorine had
not time before it was neutralised to kill the organism present
in the bisulphite of soda solution. This of course afforded an
explanation of the irregular results obtained in the preceding
series. Even on the third day, when excellent results were ob-
tained during the greater part of the day, acid-forming organisms,
not true Bacillus coli, were present at 12 noon and at 3.30 p.m.
The results obtained by the other bacteriologists coincided exactly
with our own—sometimes the treated water was free from Bacillus
colt in 500 c.c., at others the presence of this organism could
be demonstrated. On the next two days the amount of chlorine
was halved. During the early part of one day acid-forming
organisms were present in 500 cc. but, from this time onwards,
sterilisation was complete. During the next three days one part
of chlorine in four million parts of water was used and only once
during the whole of this time was the Bacillus coli found in
500 c.c. of water. On the last four days of the experiment one
part of chlorine in seven to eight million parts of water was used
but no bisulphite of soda was added. Of 13 samples of 500 ce.
Sterilisation Experiments on the Cambridge Water. 571
each, taken during this period, every one was sterile, no coliform
organisms being found in 64 litres of the treated water. More-
over on no single occasion was there either taste or smell of
chlorine ; the water was clear and bright, and fresh and palatable.
From these experiments I am satisfied (a) that sterilisation
of the Cambridge water by bleaching powder is not only efficient
but is easily carried out; for given the faintest trace of chlorine
in the treated water as it comes from the chlorinating cylinder at
the end of a somewhat indefinite period of treatment (more than
20 minutes) sterilisation was complete; (b) that in the case of the
Cambridge water it is unnecessary to add bisulphite of soda, the
process thus being enormously simplified; (c) that the trace of
chlorine remaining at the end of treatment disappears very rapidly
as the water passes through the pipes or as it is exposed in the
reservoir.
The amount of chlorine remaining at the end of treatment
may be readily measured by any intelligent labourer supplied
with a bottle of iodide of potassium crystals and a flask of filtered
starch ; a crystal of iodide of potassium, a few drops of acetic acid
and a tablespoonful of starch solution added to a litre of the water
in a glass jug held over a white tile or a sheet of white paper
enabling the observer to determine at once whether it has a blue
or a violet tint or is clear. If there is a deep blue tint there is
too much chlorine present; a violet tint is the proper “end re-
action” showing the presence of a faint trace of chlorine, whilst,
if there is no colour at all the amount of chlorine present is
not sufficient to ensure sterilisation. This work was carried out
mainly by my assistant, Mr Mitchell, to whom I am greatly
indebted for the careful manner in which these observations
were made. He remained at Fulbourn during the whole time
over which the experiments extended, but after a time the
engineer who looked after the pumps was detailed to make
these colour estimations. These I compared with my own and
Mr Mitchell’s estimations and found that they were in all respects
most satisfactory. This, of course, is an exceedingly important
practical detail for it is evident that the chlorine may be made to
serve as an indicator of the presence of organic matter im water.
Instead of waiting for a bacteriological examination, the simplest
and shortest of which takes several days to carry out, an estimate
of the amount of chlorine absorbed may, if necessary, be made from
hour to hour, the amount of chlorine required to give the violet
reaction at the end of contact being the amount necessary to
ensure complete sterilisation.
From these experiments then I am satisfied that from the
point of view of ease of application, certainty of action, and
absence of interference with the physical characters of the water,
572 Prof. Woodhead, The results of
this method of sterilisation is admirably suited for the treatment
of the Cambridge water and indeed of all waters where ‘the
amount of organic matter is small but which are open to suspicion
on other grounds. Even in those chalk waters in which the
amount of organic matter is variable this method may be utilised,
though in cases where the amount of decomposing organic matter
is greater the difficulty of getting rid of taste and smell may be
increased and some modification of the process may have to be
devised.
It may be asked what is the effect of this treatment on living
animal organisms. Sometime ago F. 8S. Locke* following up ex-
periments carried out by Naegeli and by Ringer and Phear+ found
that very minute quantities of copper dissolved in distilled water
had a toxic effect on tadpoles, killing them in from two to twenty-
two hours, one part of sulphate of copper in two millions of water
proving fatal. It was noted that several other heavy metals acted
in the same way. Naegeli had already pointed out that one part
of copper in seventy-seven million parts of distilled water was
fatal to Spirogyra. Chlorine in the minute quantities used in
the experiments above recorded seems to act equally powerfully
on vegetable protoplasm, but on the health of tadpoles one part of
chlorine in two million parts of tap-water has absolutely no effect,
the tadpoles remaining exceedingly lively at the end of nine or
ten days. Further it was noted that chlorine added to distilled
water actually neutralises the action of copper, iron, and tin. It
does not prevent the formation of a carbonate of lead, and tadpoles
kept in chlorinated distilled water in which has been placed a
bright strip of one of these metals remained active and vigorous
whilst tadpoles that are placed in distilled, but non-chlorinated,
water in which are placed similar strips of metal soon die. It is
interesting to note that water drawn from the laboratory tap
which has remained in the pipes for some little time proved fatal
to tadpoles in 24 hours, showing that these creatures are very
susceptible to slight changes in the water in which they are
placed. Water drawn directly from the main and which has not
remained in the pipes for any length of time has no effect upon
the tadpole, which remains perfectly lively just as it remains in
any dilution of chlorine up to one part in two millions of water
whether bright metal has been added or not. This chlorinated
water therefore is less deleterious to tadpoles than is water that
has passed through the laboratory supply pipe, water that we .
constantly drink and use for all ordinary purposes.
It is evident then that in the Cambridge water very minute
quantities of the oxy-chlorine compound are sufficient to bring
* Journ. of Physiol. London, Vol. xvitt, 1895, p. 319.
+ Journ. of Physiol. London, Vol. xvm, 1894-5, p. 423.
Sterilisation Experiments on the Cambridge Water. 573
about most efficient sterilisation, especially if the following con-
ditions are observed. The chlorine should remain in contact with
the water as long as possible; the ideal method of treatment,
therefore, would be by means of an automatic “injector” to throw
“bleach ” solution into the mains leading from the pumping wells
to the reservoir. During dry weather, the necessary amount of
chlorine once determined, the work once started and the chlorine
flow regulated, the process may be allowed to go on almost with-
out attention. During rainy weather rough tests should be made
as to the amount of chlorine absorbed from time to time. When
no colour reaction is obtained with iodide of potassium and starch
it would be necessary to increase the strength of the chlorine
solution until a reaction is obtained. This of course may be done
either by increasing the amount of “chloride of lime” added to
the solution already in the chlorine supply tanks, or by increasing
the speed of the pumping engines injecting the fluid. The test is
made in three or four minutes and any increase of organic matter
is determined at once and, in our experience, is so small that it
may always be neutralised even after the heaviest rainfal] observed
during the time our experiments were being made by an increase
of about 20°/, of chlorine, this addition invariably ensuring com-
plete sterilisation. The chlorine and water should be thoroughly
mixed in the rising main and should be conducted to a reservoir
of sufficient capacity to contain a couple of days supply. Equalisa-
tion of the chlorine would thus be obtained and the conversion
of any slight excess of chlorine into hydrochloric acid would be
ensured. Water so treated is absolutely free from organisms of
the Bacillus coli type and therefore from bacilli of the typhoid
and paratyphoid groups.
574 Mr Whiddington, Preliminary note on the
Preliminary note on the properties of easily absorbed Réntgen
Radiation. By R. WurppineTon, B.A., Allen Scholar, St John’s
College. (Communicated by Prof. Sir J. J. Thomson.)
[Received 2 August 1910.]
The present note is intended to give a brief outline of results
obtained by the writer during the course of investigating the
properties of very soft Rontgen radiation and to indicate the
direction which the research is taking.
A study of the literature bearing on primary Réntgen radiation
revealed the fact that what little work has been done on the subject
did not include quantitative investigations into the properties of
such soft radiations as are to be referred to below. Apparently
the softest radiation ever quantitatively studied is the character-
istic chromium radiation of mass absorption coefficient in
aluminium (*) 136 *,
The form of apparatus used in the experiments on the softest
radiation is indicated in the figure.
When the tube is evacuated to a convenient point a potential
applied between C and A—C being the cathode—produces a
stream of cathode rays which strike the anticathode A. A is one
* Barkla, Phil. Mag. 1909, vol. xvi. p. 749.
+ For potentials higher than 4000 volts a different form of tube is found to be
convenient.
is
properties of easily absorbed Rontgen Radiation. 575
of a series of metallic plates mounted on the magnetically
controlled carriage 7, so that any one can be brought under the
action of the cathode stream. The velocity of the cathode rays
can be varied by altering the potential applied to the tube.
The Rontgen rays produced are allowed to stream out through
the aluminium window W and are measured by the ionization
they produce in the ionization chamber J.
Absorbing screens can be introduced between NV and W.
The following are some of the more important results.
1. There is a cathode ray velocity below which no Rontgen
radiation can be detected.
2. Using cathode rays produced by a potential of 2500 volts
and over, the anticathodes arrange themselves in the following
descending order as radiators: aluminium, platinum, silver, lead,
tin, nickel, cadmium, iron, antimony, copper, zinc. Antimony has
a tendency, at greater potentials, to take a higher position in this
scale.
Aluminium at these low potentials is about five times as
efficient an anticathode as copper.
There is strong evidence in favour of the view that aluminium
and platinum give out characteristic secondary radiations. The
mass absorption coefficient (~) in aluminium is about 600.
3. There is reason to believe that this secondary radiation
can be excited by a primary radiation somewhat less penetrating
than itself.
4. The emission of the secondary radiation from aluminium
and platinum is accompanied by corpuscular emission.
The investigation is being continued to higher potentials.
576 Mr Brindley, Further notes on the
Further notes on the procession of Cnethocampa pinivora. By
H. H. Brinpey, M.A., St John’s College.
[Read 6 June 1910. ]
[Plates XIII, XIV.]
In October 1906 I described to the Philosophical Society
some observations made at Arcachon in the previous April on
the processional habit of the larvae of the Eupterotid moth
Cnethocampa pinivora (Proc. Camb. Phil. Soc., 1907, xtv. Pt. 1.
p. 97). In this paper I referred to the work already published
on the subject from the pioneer observations of Réaumur in 1736
to the account of the life history of the moth given by Fabre
in 1898 (Souvenirs Entomologiques, Série vi.), which is our chief
source of information. It is unfortunate that this work, so
delightful for its literary beauty, often fails the reader in
exactness and statistical detail. The moth lives entirely among
the pines of the Landes (where the tree is chiefly Pinus pinaster)
and other districts of southern France. The eggs are deposited
in cylindrical clusters on the young leaves of the pine, hatching
occurs in September and the offspring of one parent construct
a silk nest in the branches. Feeding and enlargement of the nest
take place during the winter months, and on warm days in late
March and early April excursions are made in procession from the
nest tree over the sand. Burrowing for pupation concludes the
last procession. The imagos appear in August and live only
a short time, how long exactly is still uncertain, but Fabre’s
account indicates that the eggs are laid a few days after the adult
stage is reached. The procession is in single file and each larva
secretes a thread which Fabre holds to be the guide for return to
the nest tree.
The accounts of Réaumur, Ratzeburg (1840), and Fabre and
my own observations in 1906 left certain points about the
procession in doubt, and last year Mr T. G. Edwards of Emmanuel
College, at my suggestion, went to Arcachon and examined many
processions between March 18th and 31st. Huis observations are
recorded in the Proceedings, 1910, xv. Pt. v. p. 483. I visited
Arcachon again from March 29th to April 5th of the present year,
but was unfortunate in the weather, for it was unusually cold for
the region in April, two days presenting the exceptional event of
snow squalls, which kept the larvae in their nests. On no day
could I discover any processions in the woods, though, except
on the coldest days, larvae were to be found on the march in the
Allée de Turenne, which is a sheltered road of villas in gardens
~
procession of Cnethocampa pinivora. 577
with many pines, descending to the entrance of the actual forest.
Mr Edwards informs me that most of the processions and the
longest individual ones he found were in the Allée de Turenne
in the much more favourable weather he experienced. The
comparative frequency of processions in this inhabited road is
curious, as the pines in the villa gardens are nearly all high and
nests seem relatively scarce, while they are very numerous in the
large plantation of saplings, averaging 12 ft. high, surrounded by
old pines destitute of nests a short distance within the forest.
The accompanying photographs show nests in this plantation.
I examined a large number of the nests on the saplings and did
not find one which contained more than 16 living larvae, and
this number was exceptionally high. As there was no evidence
that the nests were temporarily deserted by larvae in procession
it seemed that their occupants must have buried for pupation
before my visit, which on the whole agrees with Edwards a fortnight
earlier finding many more processions than I did. But if the forest
larvae had buried themselves it appears probable that some con-
dition holds for the Allée de Turenne which causes certain or all
the events of the life cycle to fall later than in the forest proper.
The longest processions I found in the Allée were 33 and 68 larvae
respectively. These two were close together and there were reasons
for thinking that they were a procession of 101 broken. Edwards
records one of about 260 larvae, and Fabre observed one of 300.
As stated above I found no processions in the pine forest
itself, and as prolonged observations in the Allée de Turenne were
difficult from the traffic I made collections of larvae there and
placed them on the sand in the forest. This treatment did not
interfere at all with the formation of processions, and when the
larvae were placed on a table indoors processions were made as
quickly as on the sand in the forest: thus in one case a group
of 7 larvae placed on a tablecloth were in regular march in
8 minutes.
It will be noted that the circumstances caused my obser-
vations this year to be made under less natural conditions than
those by Edwards. Again, some of them were made on members
of single processions and others on larvae of different proces-
sions mixed together. Thus some of the features noticed may
have been due to the larvae being from different nests and of
different ages, but I did not find any distinction between the
behaviour of what may be called “pure” and “mixed” processions.
Larvae certainly from different nests formed processions as readily
as those belonging to one procession. But the great tendency of
processions to break up into daughter processions recorded by all
observers and the readiness with which stray larvae will join a
procession render it impossible to regard any procession seen first
in march as belonging to one nest. This raises the important
578 Mr Brindley, Further notes on the
question as to how far the families remain separate after they
have commenced the processional habit. Continuous observa-
tion of the members of one nest from the first day of procession
is necessary to be certain on this point. Fabre does not deal
with this question definitely. He observed the larvae emerging
from the nest for a march, but does not say whether the in-
tegrity of the family was maintained from day to day. He states
however (p. 339) that daughter processions return to the nest
tree by wandering till they find the thread. The observations
by Edwards and myself suggest that this must very often fail to
happen. (Before the processional excursions begin it is probable
that the larvae remain in separate families, since it is rare to find
more than one nest in a tree.) In fact we remain in great
ignorance regarding the peculiar habit of forming processions
which return to the nest tree. That the larvae leave the tree
in a procession which may cover much ground and which ends in
burrowing for pupation is quite certain, but it remains uncertain
whether processions which return to the tree are the rule or only
exceptional. Fabre gives no statistics on this matter, but states
merely that in winter and early spring such processions do occur
on fine mild days, hazarding the suggestion that they represent
“une promenade hygiénique, un pelerinage de reconnaissance aux
environs, peut-étre un examen des lieux ot se fera plus tard
lensevelissement dans le sable pour le métamorphose.” Prima
facie such processions appear disadvantageous, for instance, apart
from other accidents such an exposed proceeding might be expected
to engender, oviposition by Tachinid flies is likely to occur, and
this event I observed in 1906, as described in my previous paper.
In spite of some degree of protection by the glandular hairs of
the larvae, which were obviously dreaded by the flies, the latter
succeeded every now and then in inserting their ovipositors. In
1909 and this year Edwards and myself saw no Tachinids, but
the sunless bleak days of my visit this year were probably un-
favourable to their activity. In the limited time at my disposal
and in the absence of opportunity of following a procession from
its departure from the nest till its return to it, I endeavoured this
year to obtain circumstantial evidence as to the occurrence of
processions which return to the nest tree. One step was the
examination of saplings bearing nests. In all cases the branches
near the nest were coated profusely, in fact matted, with the
ageregation of threads formed by the larvae, which is in accordance
with Fabre’s statement that in their nocturnal excursions from
the nest to feed on the young leaves the larvae separate, each
spinning a thread which he holds is a guide to returning to
the nest towards sunrise. Below the nest the matting over with
threads becomes less profuse, and on the trunk of the sapling
threads are rare, though in places some are seen extending
procession of Cnethocampa pinivora. 579
towards the ground. In spite of much search I never found one
reaching to the ground and very rarely within a yard from it.
There is little difficulty in seeing the thread, which glistens as it
lies adhering to the flakes of bark. Moreover it is very durable
and does not seem to suffer much from wind or rain, as shown by
the matting over of the upper branches and the durability of the
nest itself, which is essentially a winter dwelling. Again, the
thread left by a procession is the aggregate secretion of all the
larvae; Fabre calls attention to its thickness when formed by
a long procession, and Edwards records that 150 larvae may make
a thread nearly 3 mm. wide. Such a thread is very strong and
I have lifted the thread of a procession clear of the ground for two
feet without breaking it, though it was loaded with adhering sand
particles. Now the threads which I found running down the
trunks of saplings were thin ones resembling those secreted by
single larvae, and certainly did not suggest processions frequently
leaving and returning to the tree. There seemed no ground for
thinking that threads near the base of the trunk are especially
likely to be swept off accidentally, by the movements of under-
growth in wind for instance. It must be admitted that the
examination was on trees bearing in most cases deserted nests
and perhaps some unknown cause had removed the threads near
the ground since the final procession had left the tree, but if a
thread near the base lasts as long as those on the branches, that
of the final procession should have been found. But on the whole
the impression left by the threads on the bark is that the larvae
do not habitually leave the tree and return to it.
If the thread is really a guide to return to the nest tree the
leader of a homeward bound procession must make use of it
by coming across its own thread and recognising it as the one
to follow. Edwards sought for information on this point by
placing a frayed-out piece of artificial silk or the natural thread
of another procession in the leader’s path—this was disregarded
entirely. I repeated Fabre’s experiment of picking up the thread
of a procession with forceps and looping it round so as to be
encountered by the leader. On each occasion, and the experi-
ment was made with different processions, the leader crossed the
thread without regarding it more than any other small obstacle
he encountered. This accords with Fabre’s experience (loc. cit.
p. 339), when endeavouring to make the larvae march in a closed
circle. If a larva can distinguish its own thread among the
numerous ones which are seen on fine days crossing the sand
in all directions, it appears probable that it would show some
recognition of it so soon after its formation as this, even. if its
psychological condition were not in favour of a return to the nest
tree at the moment. It can only be said that much more
VOL. XV. PT. VI. 38
580 Mr Brindley, Further notes on the
‘evidence is required before we can feel certain that Fabre’s
suggestion as to the function of the thread formed during
procession can stand. It may well be that his far more extensive
study of the larvae compared with other observers justifies his
conclusion, but he does not present the evidence in the Souvenirs.
As regards the thread being a less important aid to main-
taining the integrity of a procession than head-and-tail contact
of the larvae, all that I observed is in agreement with Edwards,
who made many experiments to test the point and came to the
general conclusion that in the case of breaks in a procession
joining occurs more readily if the thread is intact, though if
the interval is short the presence of the thread seems negligible.
Only in one instance of many did it appear to me that joining up
really resulted from the larvae finding and following a thread
secreted ahead of them. A procession of 6 larvae came across
a thread formed by a single larva, when the leader of the
6 closely followed it, a proceeding which was more obvious because
the single larva went round in a circle. At the same time
the distance was only a few inches, and sight may really have
been the guide. On all the other numerous occasions on which
two processions became one or single larvae joined processions
there was no suggestion that the thread was regarded, while
on several occasions the impression that sight was the chief aid
in effecting joining up was strong. Moreover, a single larva
joining a procession does not always make contact with the last
in the procession, but just as often comes parallel to the marshalled
larvae and quickly intercalates itself between any two, being
accepted without hesitation.
In considering the value of the thread in maintaining the
integrity of a procession it is necessary to refer to the “circulating
mass,’ so frequently formed by larvae on the march. This con-
dition has been already described by Fabre (loc. cit. chap. XX, p. 332),
Edwards (loc. cit. p. 434), and myself (loc. cit. p. 100), and it is
enough to say here that the chain breaks up into a heap of larvae
walking over each other without the heap as a whole making
way over the sand. The mass formation was held by Fabre to
be encouraged by cold and darkness, and to be very likely a mode
of resting. Kdwards has discussed the subject (loc. cit. p. 434).
It is certainly the usual condition of a procession about to burrow,
but it is frequently adopted temporarily, the procession reforming
sooner or later. Artificial imterference with a procession will
often cause the formation of a mass, but it is quite unknown
why it is so frequent a condition of a group of larvae on the
march, While in a circulating mass the individuals continue to
‘ secrete threads, but the continual crossing over each other by
the larvae necessarily prevents the fusion of the threads which
procession of Cnethocampa pinivora. 581
occurs when they are in procession, so the animals are very soon
in a tangle of silk. Edwards is inclined to think that the threads
secreted in the mass may be a help towards a procession when
reformed keeping the same leader. In five different processions,
the largest of which consisted of 57 larvae, he found that the new
procession had the same leader as the old one.
I endeavoured to obtain light on the matter by observing
short processions, distinguishing the individual larvae by powdered
chalk of different colours, which, like the flour used by Edwards,
adheres well to their hirsute dorsal surface. If only a small number
of larvae are observed it is quite possible to preserve their identity
by this method; with large numbers a colour scheme naturally
breaks down. It is believed that the observations set forth below
were accurate; others which appeared faulty from one cause and
another are omitted. The times at which changes occurred are
given to convey an idea of the rapidity with which the larvae
alter their procedure. The numbers indicate individual larvae,
1, 2, 3, etc, being allotted according to their order in the first
procession of one continuous observation. ... indicates that two
larvae were not quite in contact. Each observation commenced
by placing the larvae in a heap on sand with little or no
vegetation.
I. Batch A. 5 larvae. April 2nd.
5.0 p.m. larvae put in heap.
5.5 p.m. procession 12345.
5.15 pm. larvae again put in heap.
5.22 p.m. procession 1352...4.
5.25 p.m. larvae again put in heap.
5.30 p.m. procession 253...4...1.
II. Batch A. 5 larvae. April 3rd.
10.40 a.m. larvae put in heap.
11.0 am. procession 12345.
11.10 am. larvae again put in heap.
11.15 am. procession 35142.
11.28 a.m. larvae again put in heap.
11.30 am. procession 32145.
11.34 a.m. procession 321405, 0 being a larva belonging
to another batch which had buried itself
shortly before and had just been dug up
a few inches away from the procession,
which it joined voluntarily in the position
shown.
11.35 am. larvae again put in heap.
11.45 a.m. procession 462513.
11.50 a.m. larvae again put in heap.
11.59 a.m. procession 4235 (0 and 1 had strayed away).
38—2
582
Ill. Batch A. 6 larvae.
Mr Brindley, Further notes on the
4.45 p.m.
4.55 p.m.
5.5 p.m.
5.15 p.m.
5.20 p.m.
5.25 p.m.
5.40 p.m.
5.45 p.m.
5.54 p.m.
Veatch Aer ri
V. Batch B. 6 larvae.
VI. Batch C. 8 larvae.
A summary of the above is
1.25 p.m.
1.40 p.m.
1.45 p.m.
1.51 p.m.
3.25 p.m.
3.98 p.m.
3.45 p.m.
3.90 p.m.
3.55 p.m.
4,30 p.m.
4.40 p.m.
4.45 p.m.
4.50 p.m.
4.55 p.m.
5.0 p.m.
5.15 p.m.
5.18 p.m.
5.41 p.m.
Same leader as in
previous procession
New leader
larvae.
April 3rd.
larvae put in heap.
all burying.
burying relinquished, procession forming.
procession 123456.
larvae again put in heap.
procession 543621.
a stray larva (0) from another batch was fol-
lowed and the procession became 0...543621.
larvae massed voluntarily.
procession 2643105.
April 4th (the only indoor experi-
ment quoted).
larvae put in heap on white table-cloth.
procession 1234567.
larvae massed voluntarily.
procession certainly with another leader, but
which exactly not ascertained.
April 2nd.
larvae put in heap.
procession 123456.
larvae massed voluntarily.
procession 1342 25 26.
larvae again massed voluntarily, during
which four larvae (LLLL) from another
batch came into the group.
procession forming as 1423LL.
procession 12356LLLL(No,4had commenced
burying).
procession 1235?6L4LLL (No. 4 having
relinquished burying and intercalated).
April 3rd.
larvae put in heap.
some or all burying.
burying relinquished, procession forming.
procession 12345LLL (last three not marked
with colours).
larvae put in heap.
procession 1L2L35L.
Number of cases
After voluntary After artificial Total
massing massing
2 4 6
2 4 6
procession of Cnethocampa pinivora. 583
In this there is little or no suggestion that the threads secreted
in the circulating mass help to preserve the order of a procession,
for even if the threads of individual larvae are secreted continuously
in a voluntary mass they are certainly broken when the mass is
made artificially. Edwards (loc. cit. p. 435) suggests that the formation
of a mass may be a means of altering the order of the larvae while
retaining the same leader, but there seems to be little evidence for
this view.
Moreover the mass formation may continue for an hour or two
before a new procession is formed, and as threads continue to
be secreted the larvae are in a tangle of silk after a prolonged
massing, in which it seems impossible any individual thread can
be distinguished by them. It is true that the number of cases
in which the old leader was retained is, both in Edwards’ and my
own cases, higher than mere chance would give, and a possible
explanation is that in any procession one larva has a greater
tendency to stray than the others, and this one is thus more likely
to act as leader. I found that it is not at all uncommon for one
larva to stray from a mass and to repeat this again and again
when put back artificially. Such specially erratic larvae secrete
a thread but it is disregarded by the others. These independent
larvae sometimes return to the mass voluntarily after an excursion
several inches away. In this case and also if put back artificially
they are often seen to relinquish the wandering and to take any
place in a new procession. It may be suggested that the pro-
cession is reformed from a mass by a larva with the wandering
habit relatively marked tending to leave it, while the other larvae,
as can always be seen when a procession forming is watched, in the
endeavour to retain contact become parallel with it, at the same
time falling behind because it walks faster. One of its fellows
thus soon finds its head in contact with the leader’s tail, which
is the processional position. The same thing happens for all the
larvae in succession and these fall from two or three abreast into
single file till the new procession is fully arranged. Processions
are invariably formed by the larvae coming into head-and-tail
contact in succession. I have never seen them make head-and-tail
contact simultaneously with their bodies bent and then the
procession gradually straighten. What happens is that the pro-
cession emerges as a straight line from a continuously diminishing
circulating mass.
The above observations suggest that the thread is of very little
or no value in the formation of a procession, and that its help
in maintaining the integrity of a procession is slight. It seems
to be secreted all the time that larvae are in active movement,
whether on the march, in mass or burying. It forms the nest
in the tree and the cocoon of the pupa state. Why its secretion
584 Mr Brindley, Further notes on the
should continue when the larvae are feeding and when they are
away from the nest tree remains obscure, and at present Fabre’s
ingenious suggestions as to its value can be regarded only as
surmises. The great expenditure of material and energy which
its formation involves we have no right to call useless. It is
possible of course that it is to some extent an excretory process,
and we know that sericin and fibroin, which occur in silk, like the
other skeletins of invertebrate animals, contain nitrogen (Schafer,
Text Book of Physiology, 1898, 1. p. 76).
As far as I could ascertain a larva marching alone secretes
a thread almost invariably. That of a single larva is very fine,
but careful examination of the sand in its track with a lens shows
it: even this single thread is strong enough to be lifted for an
inch or two without breaking in spite of the particles of sand
adhering to it. A fairly extensive enquiry on this point revealed
only three or four cases of larvae marching without making the
thread.
The details of processions given above are quite in agreement
with the original statement by Fabre and the observations of
Edwards that there is no special leader: when once a procession
is formed the leading larva may be removed without interference
with the progress of march. Leadership in a particular sense
exists only in the formation of a procession from a circulating
mass. All that therefore need be said on the subject here is to
quote an experiment I made to find out with some exactness
if the removal of the leader checked the progress of a procession
at all. In the case of a procession of 6 larvae I reversed each
larva, placing it with forceps as quickly and carefully as possible
in head-and-tail contact with its neighbours, thus effecting an
artificial countermarch. The procession proceeded at once in the
direction opposite to the original one. Immediately it was well
on the march I removed the leader and placed it in contact with
the last larva, repeating this each time immediately the march
was resumed. The times given below are those when the order
was changed as stated.
5.0 pm. << 123456 5.9 pm. 4561235
52pm. 123456 5.14 p.m, 345612
5.5 pm. 612345 > 517 pm. 234561 >
5.7 pm. 5612345 5.19 pm. | 123456 >
The interval of five minutes between 5.9 and 5.14 was not due
to special hesitation of the leader, but because removing it was
delayed in order to watch the behaviour of the larvae to
sunlight, which at this time broke through the clouds. Each
time the leader was removed the new leader cast about with its
procession of Cnethocampa pinivora. 585
head in the manner characteristic of all isolated larvae and of
any larva not in contact with the tail of another, and thus it
checked the progress of the procession. In only one case did the
hesitation last for more than two minutes. In all cases the old
leader placed in head-and-tail contact with the last larva joined
up immediately. This and similar observations made on other
groups also suggest how little necessary is the thread for keeping
the integrity of a procession. The extent to which the leader for
the time being takes the initiative has been discussed by Fabre
(loc. cit. p. 337), and Edwards (loc. cit. p. 432).
The influences which determine the direction of a procession
on the march remain very obscure. Fabre (pp. 367, 368) states
his belief that sunlight is the guide, but adds “les points d’ou
vient le plus de chaleur sont les préférés.” In the case of
processions I have seen in the woods the general direction
appeared to be towards the greatest sunlight through the foliage,
and the sidewalks and roadway of the Allée de Turenne at
Arcachon in which processions are so often seen are more sunlit
than the gardens from which they come: again in the case of
processions indoors the course taken was usually towards the
window. Edwards (loc. cit. p. 432) describes how the leader of a
procession followed rays reflected artificially on to him alone.
This year, April 4th afforded the only favourable opportunity
I had of observing the possible effect of sunlight, as that was the
one day of sunshine, bright intervals occurring between showers.
Two short processions of three larvae each and a single procession
resulting from artificial mixing of these certainly did not march
towards the sun. The general direction taken was either at right
angles to the path of sunlight or away from the light. In one
case the sudden breaking out of light from between clouds was
at once followed by the procession of six turning away from it.
In this and on other occasions attempts to make the processions
march towards the sun failed altogether. These processions were
on sand clear of trees, but from 10 to 20 feet away from a zone
of saplings. The latter were away from the sun and the general
direction of the larvae was towards them. Whether smell or other
sense attracted the larvae towards the trees cannot be asserted,
but they certainly did not follow the path of greatest light. We
remain in ignorance of the stimuli which influence the behaviour
of a procession. The remarkable dorsal papillae of the larvae
may be “appareils de météorologie” as Fabre has suggested
(loc. cit. p. 366), and in various respects it is likely that the larvae
respond to influences we cannot comprehend.
Burying for pupation has been described in detail by Fabre (Joc.
cit. pp. 368, 369) and also by Edwards (loc. cit. p. 435). I watched
it frequently this year and found that as a rule all the larvae of a
586 Mr Brindley, Further notes on the
circulating mass beginning to burrow together occurred much more
frequently than the leader checking a procession by commencing
to burrow and its followers doing so after an interval. I may here
add to the descriptions already given of the action of a larva
burying itself that the chief movement of the body is dorso-
ventral bending as the sand is attacked with the mandibles, and
that the hind end of the body and the prolegs are the chief means
of bringing the excavated sand to the surface. The true legs seem
to shovel the loosened sand back to the prolegs. In one imstance
in which the leader of a procession of seven commenced burrowing
its example was not followed. The second larva partially descended
the hole made by the leader but did not burrow. This continued
for 20 minutes, when the remaining six larvae marched away in
two processions of three each. The leader had quite buried itself
in 31 minutes. In two sets of observations on the same group of
larvae earlier in the day this particular larva had been remarked
as erratic and repeatedly straying from its fellows.
I do not know any published statements on the time which
elapses between the beginning of burrowing and complete burial,
so I may mention that single larvae were seen to bury in 31 and
37 minutes, a group of 4 in 110 minutes, one of 7 in 120 minutes,
one of 12 in 85 minutes, and one of 21 in 110 minutes. Seven
larvae which had been buried for 48 hours were dug up; one of
these completely reburied itself in 10 minutes and the other six
did so in 40 minutes. These larvae were from 3 to 4 inches deep
when first dug up and appeared to have added very little silk in
the two days. Fabre indicates that the cocoon is completed in
fifteen days. I brought a number of larvae, some of which had
buried themselves by April 2nd, in a biscuit box filled with sand
to Cambridge. The journey did not appear to interfere with
pupation, as by April 15th several had apparently completed their
cocoons. The imagos began to emerge from the sand on August
16th, and I placed them on a sapling of Pinus pinaster covered
with muslin in the hope that they would pair and lay their eggs
on the young leaves, but none of the moths lived long enough
to do so.
While at Arcachon the larvae I kept in boxes refused to feed
on young pine leaves, but seemed quite as active after several days
starvation as when captured. Possibly feeding is given up as the
time for pupation approaches.
As in 1906 and in agreement with Edwards’ experience
I experienced no iritation from handling the larvae. No doubt
sensibility to the glandular hairs varies with the individual:
Fabre’s own case, so vividly described (loc. cit. p. 378), is probably
exceptional.
Very much concerning the processional habit remains obscure.
procession of Cnethocampa pinivora. 587
Réaumur and all subsequent authors observed the larvae to a
considerable extent under somewhat artificial conditions. Even
in Fabre’s glass-houses containing pine saplings and sand at
Sérignan the larvae could not wander as much as in the woods.
The really satisfactory method would be to follow day and night
the proceedings of the occupants of a nest in the woods. This
would throw light on how far they can range and yet find their
nest again and to what extent the integrity of a family is
maintained. The meaning of processions which do not end by
burying and the advantage obtained by continuous secretion of
the thread remain puzzles. So also does the frequent formation
of a “circulating mass” by a procession. It seems certain that
contact between larvae is of much importance and that though
there is no permanent leadership the leader for the time being
does really determine the behaviour of a procession because all
its followers endeavour to maintain head-and-tail contact. This
is seen well when the leader checks its march, for the larvae
always endeavour to maintain head-and-tail contact by bending
their bodies: overlapping ensues only if the leader stops for some
little time. Thus mass formation is always incepted by the leader,
as sometimes also is burrowing.
In my previous paper I suggested that the procession may be
compared with a chain of salps or polychaetes, save that organic
union is absent, in the sense that they probably all respond
fairly equally to the same stimulus, hunger, sunlight, desire to
pupate and so on. The observations made since this was written
seem to emphasise the comparative importance of the leader for
the time being.
I am indebted to Mr Edwards for much information on various
matters referred to in his paper and to my wife for continuous
assistance during the observations made this year.
LITERATURE.
Réaumur, 1736, Mémoires pour Vhistoire des Insectes, 11. pp. 149—161
Paris).
Ratzeburg, 1840, Forst-Insecten, 11. p. 128, and Taf. 8 (Berlin) ; also
Stettiner Entomologische Zeitung, p. 40.
Lapaury, 1876, Ann. Soc. Ent. de France, xvi. p. 244 (Paris).
Fabre, circa 1898, Souvenirs Entomologiques, Sér. vi. pp. 298—392
(Paris).
Brindley, 1906, Proc. Cambridge Phil. Soc. xiv. Pt. 1. p. 97.
Edwards, 1910, Proc. Cambridge Phil. Soc. xv. Pt. v. p. 431.
Phil. Soc. Proc xv. Bt. Vi. Puate XIII.
oo
RON
Fig. 1. Nest of Cnethocampa pinivora on Pinus pinaster,
Arcachon, Gironde; April 4, 1910.
ai ee aie
air
Comes de
t
Sith
‘
iy)
Phit. Soc. Proc. xv. Pt. vt. PLATE XIV.
Fig. 2. Nest of Cnethocampa pinivora on Pinus pinaster,
Arcachon, Gironde; April 4, 1910.
PROCEEDINGS AT THE MEETINGS HELD DURING
THE SESSION 1909—1910.
ANNUAL GENERAL MEBRTING.
October 25th, 1909.
In the Optical Lecture Room.
Dr Hoerson, Vick-PREsIDENT, IN THE CHAIR.
The following were elected Officers for the ensuing year :
President :
Prof. Bateson,
Vice-Presidents :
Dr Hobson.
Dr Fenton.
Prof. Seward.
Treaswrer :
Prof. Newall.
Secretaries :
Mr A. E. Shipley.
Dr Barnes.
Mr A. Wood.
Other Members of the Council:
Dr Duckworth.
Mr W. G. Fearnsides.
Dr Sell.
Mr W. E. Dixon.
Prof. Wood.
Prof. Hopkinson.
Mr G. H. Hardy.
Prof. Sir J. Larmor.
Prof. Biffen.
Prof. Pope.
Mr R. H. Rastall.
Mr K. Lucas.
590 Proceedings at the Meetings.
The following Communications were made:
1. Discussion of a difference equation relating to the tension of
overhead wires supported by equidistant poles. By A. A. Ross, M.A.,
St John’s College.
2. Note on the abnormal pair of appendages in Lithobius. By
F. G. Srvcuair, M.A., Trinity College.
3. A Class on Integral Functions. By J. E. Lirritewoop, B.A.,
Trinity College.
4. On the Scattering of the B-rays from Radium by Air. By
J. A. Crowtuer, M.A., St John’s College.
5. Note on the electrical behaviour of fluorescing iodine vapour.
By R. Wuippineron, B.A., St John’s College. (Communicated by
Professor Sir J. J. Thomson.)
6. On the reflection of sound at a paraboloid. By Rev. H. J.
SHARPE.
7. On the emission of Réntgen rays from thin metallic sheets.
By G. W. C. Kayes, B.A., Trinity College. (Communicated by
Professor Sir J. J. Thomson.)
8. The emission of positive rays from heated phosphorus com-
pounds. By F. Horton, M.A., St John’s College.
November 8th, 1909.
In the Cavendish Laboratory.
ProFressor Bateson, PRESIDENT, IN THE CHAIR.
The following was elected a Fellow of the Society :
J. C. F. Fryer, B.A., Gonville and Caius College.
The following Communications were made :
1. Discontinuities in Light Emission. By N. R. CampBext, M.A.,
Trinity College.
2. The Shape of Beams of Canal Rays. By J. A. Oranes, B.A.,
Trinity College. (Communicated by Professor Sir J. J. Thomson.)
3. The determination of solutions of the equation of wave motion
which involve an arbitrary function of three variables which satisfies a
partial differential equation. By H. Barrman, M.A., Trinity College.
4, On the Oscillations of Superposed Fluids. By H. J. PRigsTLey.
(Communicated by Mr W. Welsh.)
Proceedings at the Meetings. 591
5. The stresses in a thick hollow Cylinder subjected to internal
pressure. By L. B. Turner, B.A., King’s College. (Communicated
by Professor Hopkinson.)
6. The theory of the motion of a charged particle through a gas.
By Professor Sir J. J. THomson.
November 22nd, 1909.
In the Botany School.
The following were elected Fellows of the Society :
S. Brodetsky, B.A., Trinity College.
T. K. Shaw, B.A., Sidney Sussex College.
The following Communications were made:
1. Aldabra and neighbouring islands. (Illustrated with Lantern
slides.) By J. C. F. Fryer, B.A., Gonville and Caius College.
2. Western Indian Ocean. (Illustrated with Lantern slides.)
By Professor STANLEY GARDINER.
3. Notes on the Larger Cetacea. By D.G. Lititz, B.A., St John’s
College. (Communicated by Mr A. E. Shipley.)
4, The continuations of functions defined by generalised hyper-
geometric series. By G. N. Warson, B.A., Trinity College.
5. Onsome general Properties of Mixed Solutions. By L. Vecarp.
(Communicated by Professor Sir J. Larmor.)
January 24th, 1910.
In the Optical Lecture Room.
Dr Hopson, VicE-PRESIDENT, IN THE CHAIR.
The following Communications were made:
1. On the velocities of diffusion of solutions of rubidium and
caesium chlorides. By G. R. Mines, M.A., Sidney Sussex College.
2. Experimental Investigation as to Dependence of the Weight
of a Body on its state of Electrification. By L. SourHerns. (Com-
municated by Professor Sir J. J. Thomson.)
3. Note on an Attempt to Detect a Difference in the Magnetic
Properties of the Two Kinds of Ions of Oxygen. By Miss D. B.
Pearson. (Communicated by Professor Sir J. J. Thomson.)
592 Proceedings at the Meetings.
February Tth, 1910.
In the Botany School.
PROFESSOR BaTESON, PRESIDENT, IN THE CHAIR.
The following were elected Fellows of the Society :
D. Thoday, M.A., Trinity College.
R. H. Compton, B.A., Gonville and Caius College.
H. Hamshaw Thomas, B.A., Downing College.
The following Communications were made:
1. A note on some fossil plants from Newfoundland. (Illustrated
by lantern slides.) By E. A. Newein Arser, M.A., Trinity College.
2. On the relation between the fossil Osmundaceae and the
Zygopterideae. (Illustrated by lantern slides.) By W. T. Gorpon.
(Communicated by Mr E. A. Newell Arber.)
3. Ona new species of Physostoma from the Lower Carboniferous
of Pettycur (Fife). (Illustrated by lantern slides.) By W. T. Gorpon.
(Communicated by Mr E. A. Newell Arber.)
4. A note on Cardiocarpon compressum Will. By Mrs HE. A.
NEWELL ARBER. (Communicated by Mr E. A. Newell Arber.)
5. On the assimilating tissues of certain Coal Measure plants.
(Illustrated by lantern slides.) By H. Hamsoaw Tuomas, B.A.,
Downing College. (Communicated by Mr E. A. Newell Arber.)
6. Notes on the genus Schizoneura Schimper and Mougeot. By
L. J. Wiuts, M.A., King’s College. (Communicated by Mr E. A.
Newell Arber.)
7. On the occurrence of Schizoneura paradoxa S. and M. in the
Bunter of Nottingham. By R. D. Vernon. (Communicated by
Mr E. A. Newell Arber.)
8. On petrified plant remains from the Upper Coal Measures of
Bristol. By D. G. Lituis, B.A., St John’s College. (Communicated
by Mr E. A. Newell Arber.)
Proceedings at the Meetings. 593
February 21st, 1910.
In the Comparative Anatomy Lecture Room.
PRoFESSOR SEWARD, VICE-PRESIDENT, IN THE CHAIR.
The following were elected Fellows of the Society :
A. B. Bruce, M.A., Peterhouse.
F. W. Dobbs, M.A., Trinity College.
The following were elected Associates :
R. T. Beatty, Emmanuel College.
W. T. David, Trinity College.
S. G. Lusby, Emmanuel College.
The following Communications were made:
1. Mimicry in Ceylon Rhopalocera, with some notes on the
enemies of Butterflies. (Illustrated by lantern slides.) By Professor
PUNNETT.
2. The Andaman Islands. (Illustrated by lantern slides.) By
A. R. Brown, M.A., Trinity College. (Communicated by Mr A. E.
Shipley.)
3. The Procession and Pupation of the larva of Cnethocampa
pimvora, By T. G. Epwarps, B.A., Emmanuel College. (Communi-
cated by Mr H. H. Brindley.)
4. On Double Sixes. By Professor W. BurnsIDeE.
5. The solution of a system of Differential Equations occurring
in the theory of radio-active transformations. By H. Bateman, M.A.,
Trinity College.
6. On the Change of Order of Integration in an improper repeated
Integral. By Dr Young.
7. The production of cathode particles by homogeneous Réntgen
Radiations. By R. T. Bearry. (Communicated by Professor Sir J. J.
Thomson. )
8. On the scattering of rapidly moving electrified particles by
matter and its application to determine the number of corpuscles in
the atoms of the chemical elements. By Professor Sir J. J. THomson.
594 Proceedings at the Meetings.
March 14th, 1910.
In the Cavendish Laboratory.
ProFrssor BATESON, PRESIDENT, IN THE CHAIR.
The following were elected Fellows of the Society :
J. Romanes, B.A., Christ’s College.
EK. M. Wellisch, B.A., Emmanuel College.
L. J. Wills, M.A., King’s College.
* The following Communications were made:
1. On the cause of the phosphorescence of the glass in vacuum
tubes when the pressure is not very low. By Professor Sir J. J.
THoMsoN.
2. Transmission of B-rays. By J. A. Crowruer, M.A., St John’s
College.
3. Secondary X-Rays from Metallic Salts. By J. L. Guasson.
(Communicated by Professor Sir J. J. Thomson.)
4, Some experiments on Jonisation in dried Air. By 8. G. Lussy.
(Communicated by Professor Sir J. J. Thomson.)
May 9th, 1910.
In the Chemical Laboratory.
Proressor BATEson, PRESIDENT, IN THE CHAIR.
The President moved from the chair that in consequence of the
lamented death of His Majesty King Edward VII, the Society do
now adjourn, without transacting the business of the Meeting; and
that the Papers put down for reading be postponed till Monday,
May 23rd.
Proceedings at the Meetings. 595
May 23rd, 1910.
In the Chemical Laboratory.
Dr Fenton, VicE-PRESIDENT, IN THE CHAIR.
The following was elected a Fellow of the Society :
C. E. Raven, B.A., Emmanuel Oollege.
The following were elected Associates :
H. T. Swain, Emmanuel College.
T. Harris, Emmanuel College.
The following Communications were made:
1. The Resolution of Externally Compensated Bases into their
optically active components. By Professor Pore and J. Reap.
2. The Resolution of Dihydropapaverine. By Professor Pope and
C. 8. Gipson.
3. Further study of the Products of Chlorination of a-Picoline.
By Dr Ss x1.
4. Formation of uric acid derivatives. By Dr Fenton and
W. A. R. Wiixs, B.A., Gonville and Caius College.
5. On Water of Crystallisation in Calcium Phosphate. By
C. T. Heycock, M.A., King’s College.
6. (1) The Diketopyrrolines and their analogues. (2) The for-
mation of a- and y-pyrones from acetylenic acids. By 8S. Runmmann,
M.A., Gonville and Caius College.
7. The reduction of nitrosyl chloride. By H. O. Jonss, M.A.,
Clare College, and J. K. Matrurws, B.A., Downing College.
8. Absorption of bromine by lime. By W. A. R. Wiiks, B.A.,
Gonville and Caius College. (Communicated by Dr Fenton.)
9. Note on the adsorption of acids by carbohydrates. By F.
Rosinson, B.A. (Communicated by Dr Fenton.)
10. A hollow vortex in a polygon. By Sir George GREENHILL.
11. On a dissymmetry in the emission of cathode particles excited
by homogeneous Réntgen radiation. By R. T. Bearry. (Communi-
cated by Professor Sir J. J. Thomson.)
12. Note on the transmission of B-rays. By J. A. CRowTHER,
M.A., St John’s College.
13. On the Mobilities of the Ions produced in Air by Ultra-Violet
Light. By A. Lu. Hugues. (Communicated by Professor Sir J. J.
Thomson.)
VOL. XV. PT. VI. 39
596 Proceedings at the Meetings.
June 6th, 1910.
In the New Medical Schools.
PRoFEssoR BATESON, PRESIDENT, IN THE CHAIR.
The following Communications were made:
1. Further notes on the procession of Cnethocampa pinivora.
(Illustrated by Lantern slides.) By H. H. Brinpiey, M.A., St John’s
College.
2. The habits of Musca domestica. (Illustrated by Lantern slides.)
By Dr Granam-SmItH.
3. On the development of 7rypanosoma lewisi in the Rat flea.
By Dr N. H. Swe.LenGreBet and C. Srrickianp, B.A. (Communi-
cated by Professor Nuttall.) .
4. The absorption of tetanus toxin. By Dr F. Ransom. (Com-
municated by Mr W. E. Dixon.)
5. The fate of uric acid in the dog and rabbit. By Haroip
Ackroyb, M.B. (Communicated by Mr W. E. Dixon.)
6. The absence of living Tubercle Bacilli in old tuberculous
lesions. By Dr Conserv.
7. The action of potash salts taken by the mouth. By W. E.
Dixon, M.A., Downing College. ;
8. The results of sterilization experiments on the Cambridge
water. By Professor Sims WoopHEAD.
9. On Accident in Heredity, with special reference to Right- and
Left-Handedness. By F. J. M. Srrarron, M.A., Gonville and Caius
College, and R. H. Compron, B.A., Gonville and Caius College.
10. On Right- and Left-Handedness in Barley. By R. H.
Compton, B.A., Gonville and Caius College.
ll. The development of Gnomonia erythrostoma, the cause of the
Cherry Leaf Scorch disease. By F. T. Brooks, M.A., Emmanuel
College.
12. Jacobi’s double-residue theorem in relation to the theory of
point-groups. By Dr A. C. Drxon.
13. Discontinuities in Light Emission, II. By N. R. Campsett,
M.A., Trinity College.
INDEX TO THE PROCEEDINGS,
with references to the Transactions.
Absorption of Bromine by Lime (WILKS), 526.
Absorption spectra of concentrated and diluted solutions of chlor ophyll
d (Purvis), 85.
Absorption spectra of mesitylene and trichloromesitylene (PURVIS), 89.
Absorption spectra of solid tetramethylpicene and of its solutions (PURVIS
and Homer), 82.
Absorption spectra of various permanganates (PURVIS), 247.
Acids, Adsorption of, by Carbohydrates (Roprinsoy), 548.
AckroyD, H., The fate of uric acid in the dog, 547.
Adsorption of Acids by Carbohydrates (ROBINSON), 548.
Aldabra and neighbouring Islands (FRYER), 340.
Alpha Picoline, Products of Chlorination of (SELL), 546.
Anthocyanin, On the nature of (WHELDALE), 137.
Arper, E. A. N., A note on Cardiocarpon compressum, Will., 393.
A note on some fossil plants from Newfoundland, 390.
Argas persicus, Presence of anticoagulin in the salivary glands (NUTTALL), 53.
Bacteria, A so-called “sexual” method of forming spores in (DOBELL), 91.
Batts, W. L., Elected Fellow 1909, February 8, 294.
BARKLA, C. G., Phenomena of X-Ray Transmission, 257.
Barley, Right- and Left-Handedness in (Compron), 495.
Bases, Resolution of Externally Compensated (Pope and READ), 545.
Bateman, H., The solution of a system of differential equations occurring in
the theory of radio-active transformations, 423.
— The solution of Linear Differential Equations by means of Definite
Integrals, 294. See Transactions Xx.
— The determination of solutions of the equation of wave motion which
involve an arbitrary: function of three variables which satisfies a partial
differential equation, 590. See Transactions xxi.
Beams of canal- -rays, On the shape of (ORANGE), ; eae
Beary, R. T., Elected Associate 1910, February 21, 593.
39—2
598 Index.
Bearrty, R. T., The production of Cathode Particles by Homogeneous Réntgen
Radiations, 416.
—— Ona Dissymmetry in the Emission of the Cathode Particles which are
produced by Homogeneous Réntgen Radiations, 492.
Beta rays, The Scattering of the, from Radium by Air (CROWTHER), 273.
Beta rays, The Transmission of (CROWTHER), 442.
BouLencsEr, C. L., On the migration of the thread-cells of Marisza, 180.
Brinbuey, H. H., Further notes on the procession of Cnethocampa pinivora,
576.
BRoDETSREY, S., Elected Fellow 1909, November 22, 591.
Bromine, Absorption of, by Lime (WILKs), 526.
Brooks, F. T., The Development of Gnomonia erythrostoma, the Cause of
Cherry Leaf Scorch Disease, 534.
Bruce, A. B., Elected Fellow 1910, February 21, 593.
BurNsIDE, W., On a configuration of twenty-seven hyper-planes in four-
dimensional space, 71.
— On double-sixes, 428,
Calamostachys binneyana, On a specimen of the cone (THOMAS), 236. .
Cambridge Water, Sterilisation Experiments on the (WooDHEAD), 559.
CaMPBELL, N. R., The Radio-activity of Rubidium, 11.
—— The study of discontinuous phenomena, 117.
—— Discontinuities in Light Emission, 310.
Discontinuities in Light Emission, II, 513.
Cardiocarpon compressum, Will. (ARBER), 393.
Cathode in a discharge tube, Some fatigue effects of the (WHIDDINGTON), 183.
Cathode Particles, Production of, by Homogeneous Réntgen Radiations
(Beatty), 416.
Cathode Particles produced by Homogeneous Réntgen Radiations (BEATTY),
492.
Cetacea, Notes on the Larger (LILits), 347.
Cuittock, C., The Migration Constants of Dilute Solutions of Hydrochloric
Acid, 55.
Chlorination of a-Picoline, Products of (SELL), 546.
Chlorophyll, Absorption spectra of concentrated and diluted solutions of
(Purvis), 85.
Cnethocampa pinivora, The procession of (BRINDLEY), 576.
Cnethocampa pinivora, Procession and Pupation of the Larva of (EDWARDS),
431.
Coal Measure Plants, The assimilating tissues of some (THomas), 413.
Copsett, L., The Absence of Living Tubercle Bacilli from some Old Tuber-
culous Lesions in Man, 536.
Compton, R. H., Elected Fellow 1910, February 7, 592.
On Right- and Left-Handedness in Barley, 495.
Compton, R. H. and Stratton, F. J. M., On Accident in Heredity, with
special reference to Right- and Left-Handedness, 507.
Index. 599
CrowtHEr, J. A., Elected Fellow 1909, February 22, 295.
—— On the Relation between Ionization and Pressure for Réntgen Rays in
different Gases, 34.
— On the Relative Ionization produced by Réntgen Rays in different
Gases, 38.
—— On the secondary Réntgen radiation from air and ethyl bromide, 101.
—— On the Scattering of the B-rays from Radium by Air, 273.
—— On the Transmission of B-rays, 442.
Cubic surface in space of four dimensions (RICHMOND), 116.
Davin, W. T., Elected Associate 1910, February 21, 593.
Differential equations, The solution of a system of, occurring in the theory
of radio-active transformations (BATEMAN), 423.
Dihydropapaverine, Resolution of (PopE and Gipson), 545.
Discontinuous Phenomena, Study of (CAMPBELL), 117.
Drxon, A. C., On a property of summable functions, 210.
—— Jacobi’s double-residue theorem in relation to the theory of point-
groups, 472.
Dixon, G., Elected Fellow 1909, March 8, 295.
Drxon, W. E. and Hamitt, P., The mode of action of specific substances, 54
Drxon, W. E. and Harvey, W. H., The action of specific substances in
toxaemia, 54,
Doses, F. W., Elected Fellow 1910, February 21, 593.
DoBELL, C. C., On a so-called “sexual” method of forming spores in Bacteria
91.
Doncaster, L., Note on an abnormal pair of appendages in Lthobius, 178.
Double-sixes (BURNSIDE), 428.
Epwarps, T. G., On the Procession and Pupation of the Larva of Cnetho-
campa pinivora, 431.
Electric Detector for Electromagnetic Waves (WELLISCH), 337.
Electric Force along the Striated Discharge, The distribution of (THomson), 70.
Electricity, The Carriers of the Positive Charges of, emitted by hot wires
(THomson), 64.
Electrified Particles, The Scattering of rapidly moving (THomson), 465.
Electrometer, A string (Lasy), 106.
Fenton, H. J. H. and Ropinson, F., Homologues of furfural, 182.
Fenton, H. J. H. and Wings, W. A. R., Formation of uric acid derivatives,
547.
Fluids, Oscillations of Superposed (PRIESTLEY), 297.
Fluorescing iodine vapour, Electrical behaviour of (WHIDDINGTON), 189.
Fossil plants from Newfoundland (ARBER), 390.
Fryer, J. C. F., Elected Fellow 1909, November 8, 590.
—— Aldabra and neighbouring Islands, 340.
Furfural, Homologues of (FENTON and Rosinson), 182.
600 Index.
Gamma rays, Ionisation with (VEGARD), 78.
Gamma rays, The nature of the ionisation produced in a gas be (KLEEMAN),
169.
Gipson, C. S. and Porn, W. J., The Resolution of Dihydropapaverine, 545.
Guasson, J. L., Secondary Réntgen Rays from Metallic Salts, 437.
Gnomonia erythrostoma, The development of (Brooks), 534.
Gorpon, W. T., On the relation between the fossil Osmundaceae and the
Zo sapieidlens, 398.
— On a new species of Physostoma from the Lower Carboniferous Rocks
of Pettycur (Fife), 395.
Gravitation, The Electric Theory of (THomson), 65.
Gre@ory, R. P., Note on the Histology of the Giant and Ordinary Forms of
Pr ‘onal sinensis, 239.
Hamitt, P. and Dixon, W. E., The mode of action of specific substances,
54.
Harpine, W. A., Note on two new Leeches from Ceylon, 233.
Harris, T., Elected Associate 1910, May 23, 595.
Harvey, W. H., Elected Fellow 1909, February 8, 294.
Harvey, W. H. and Drxon, W. E., The action of specific substances in
toxaemia, 54.
Hasta, H. C., Elected Fellow 1909, February 8, 294.
Helium, The radiation of various spectral lines of (Purvis), 45.
Henry, A., Elected Fellow 1908, November 9, 292.
Heredity, On Accident in, with special reference to Right- and Left-
Handedness (Stratton and Compton), 507.
Hinz, A. V., Note on the use of the experimental method of the relative
velocities of diffusion in aqueous solutions of rubidium and caesium
chlorides, 387.
Homer, A. and Purvis, J. E., The absorption spectra ef solid tetramethyl-
picene and of its solutions, 82.
Horton, F., The emission of positive rays from heated phosphorus com-
pounds, 329.
Huaeues, A. Lu., On the Mobilities of the Ions produced in Air by Ultra-
Violet Light, 483.
Hydrochloric Acid, The Migration Constants of Dilute Solutions of (CarTrock),
55.
Hyper-planes in four-dimensional space, On a configuration of twenty-seven
(BURNSIDE), 71
Interference fringes with feeble light (Taytor), 114.
Iodine vapour, Electrical behaviour of fluorescing (WHIDDINGTON), 189.
Tonisation in Dried Air (Lussy), 459.
Tonisation with y-rays (VEGARD), 78.
Ionisation produced in a gas by y-rays (KLEEMAN), 169.
Tonisation produced by Roéntgen Rays in different Gases (CROWTHER), 38.
Index. 601
Tonisation and Pressure for Réntgen Rays in different Gases, the Relation
between (CROWTHER), 34. .
Ions formed in Gaseous Media, Mobility and Diffusion of the (WELLISCH), ile
Ions produced in Air by Ultra-Violet Light, The Mobilities of the (HucHus),
483.
Ions through a Gas, Theory of the motion of charged (THomson), 375.
Ions of Oxygen, An attempt to Detect a Difference in the Magnetic Properties
(PEARSON), 373.
Jacobi’s double-residue theorem in relation to the theory of point-groups
(Drxon), 472.
Jongs, H. O., A coloured thio-oxalate, 94.
Jonss, H. O. and Marruews, J. K., Note on the Reduction of Nitrosyl
Chloride, 529.
Kathode region, On certain phenomena of the (ORANGE), 217.
Kayr, G. W. C., The Emission of Réntgen Rays from thin Metallic Sheets,
269.
Kireman, R. D., The nature of the ionisation produced in a gas by y rays,
169.
Lasy, T. H., A string electrometer, 106.
Leeches from Ceylon (HARDING), 233.
Leucocytes in vitro, The examination of living (PONDER), 30.
Light Emission, Discontinuities in (CAMPBELL), 310.
Light Emission, Discontinuities in, II. (CAMPBELL), 513.
Lititz, D. G., Notes on the Larger Cetacea, 347.
— On Petrified Plant Remains from the Upper Coal Measures of Bristol,
411.
Lithobius, Abnormal pair of appendages in (DONCASTER), 178.
Lithobius, Abnormal pair of appendages in (SINCLAIR), 235.
LittLewoop, J. E., Elected Fellow 1909, January 25, 293.
—— A Class of Integral Functions, 590. See Zransactions xX1.
Lussy, S. G., Elected Associate 1910, February 21, 593.
—— Some Experiments on Jonisation in Dried Air, 459.
MacManon, P. A., The Operator Reciprocants of Sylvester's Theory of
Reciprocants, 292. See Transactions XX1.
Magnetic Properties of the Two Kinds of Ions of Oxygen (PEARSON), 373.
Marruews, J. K. and Jonrs, H. O., Note on the Reduction of Nitrosyl
Chloride, 529.
Mercer, J., Plemelj’s Canonical Form, 292. See Transactions XXt.
Mesitylene, Absorption spectra of (PURVIS), 89.
Mines, G. R., Elected Fellow 1908, November 23, 293.
—— On the relative velocities of diffusion in aqueous solutions of rubidium
and caesium chlorides, 381.
602 Index.
Mobilities of the Ions produced in Air by Ultra-Violet Light (HucHxs), 483.
Mobility and Diffusion of the Ions formed in Gaseous Media, Laws of
(WELLISCH), 1.
Merisia, Migration of the thread-cells of (BouLENGER), 180.
MorrraM, V. H., Elected Fellow 1908, November 23, 293.
Neon, The radiation of various spectral lines of (Purvis), 45.
Nitrosyl Chloride, Reduction of (Jones and MartHeEws), 529.
Noon, L., Therapeutic Inoculation for Generalised Bacterial Infections, 24.
Norra, G. H. F., The transmission of Trypanosoma lewist by fleas and
lice, 53.
—— The presence of anticoagulin in the salivary glands of Argas persicus, 53.
ORANGE, J. A., On the shape of beams of canal-rays, 334,
— On certain phenomena of the kathode region, 217.
Oscillations of Superposed Fluids (PRIESTLEY), 297.
Osmosis, Free Pressure in (VEGARD), 13.
Osmundaceae and Zygopterideae, The relation between the fossil (GoRDON),
398.
Overhead wires, supported by equidistant poles, Difference equation relating
to the tension of (RoBs), 198.
Paine, H. H., Elected Fellow 1909, February 22, 295.
Pearson, D. B., Note on an Attempt to Detect a Difference in the Magnetic
Properties of the Two Kinds of Ions of Oxygen, 373.
Permanganates, Influence of dilution on the colour and the absorption spectra
of various (PURVIS), 247.
Phenomena of the kathode region (ORANGE), 217.
Phenomena of X-Ray Transmission (BARKLA), 257.
Phosphorescence observed on the glass of vacuum tubes (THomson), 482.
Physostoma, A new species, from the Lower Carboniferous Rocks of Pettycur
(Fife), (GorDON), 395.
Plant Remains, from the Upper Coal Measures of Bristol (LiLure), 411.
PonvDER, C., On the examination of living leucocytes in vitro, 30.
Porn, W. J., Elected Fellow 1908, November 9, 292.
Porn, W. J. and Gipson, C. 8., The Resolution of Dihydropapaverine, 545.
Popz, W. J. and Reap, J., The Resolution of Externally Compensated Bases
into their Optically active components, 545.
Positive rays from heated phosphorus compounds, The emission of (Horron),
329.
Ports, F. A., Observations on the changes in the Common Shore-crab caused
by Sacculina, 96.
PrisstLey, H. J., On the Oscillations of Superposed Fluids, 297.
PRIESTLEY, J. G. and RUHEMANN,S., Action of Urethane on Esters of Organic
Acids and Mustard Oils, 181.
Primula sinensis, Histology of the Giant and Ordinary Forms (GREGORY), 239,
Index. 603
Proceedings at the Meetings held during the Session 1908—1909, 291.
” ” ” ” ” ” 1909—1910, 589.
Punnett, R. C., On the alleged influence of lecithin upon the determination
of sex in rabbits, 92. :
Purvis, J. E., The radiation of various spectral lines of neon, helium and
sodium in a magnetic field, 45.
—— The influence of dilution on the colour and the absorption spectra of
various permanganates, 247.
—— The absorption spectra of concentrated and diluted solutions of chloro-
phyll, 85.
— The absorption spectra of mesitylene and trichloromesitylene, 89.
Purvis, J. E. and Hommr, A., The absorption spectra of solid tetramethyl-
picene and of its solutions, 82.
Rabbits, The alleged influence of lecithin upon the determination of sex in
(PUNNETT), 92.
Radio-activity of Rubidium (CAMPBELL), 11.
Radium-content of the Waters of the Cam (SATTERLY), 540.
RaVEN, C. E., Elected Fellow 1910, May 23, 595.
ReaD, J. and Pops, W. J., The Resolution of Externally Compensated Bases
into their optically active components, 545.
Ricumonp, H. W., On the parametric representation of the coordinates of
points on a cubic surface in space of four dimensions, 116.
Rogp, A. A., Discussion of a difference equation relating to the tension of
overhead wires supported by equidistant poles, 198.
Rosinson, F., The Adsorption of Acids by Carbohydrates, 548.
Rosrnsoy, F. and Fenton, H. J. H., Homologues of furfural, 182.
RomMAnEs, J., Elected Fellow 1910, March 14, 594.
Rontgen Radiation, The properties of easily absorbed (WHIDDINGTON), 574.
Roéntgen Rays, Emission of, from thin Metallic Sheets (KAYE), 269.
Roéntgen Rays Transmission, Phenomena of (BARKLA), 257.
Rubidium, Radio-activity of (CAMPBELL), 11.
RUHEMANY, S. and Prizstiey, J. G., Action of Urethane on Esters of Organic
Acids and Mustard Oils, 181.
Satterty, J., Note on the Radium-content of the Waters of the Cam,
Cambridge Tap Water and some varieties of Charcoal, 540.
Scaugs, F. S., Elected Fellow 1909, February 22, 295.
Schizoneura, Notes on the genus (WILzs), 406.
Schizoneura paradoxa, Schimper, Occurrence of, in the Bunter of Nottingham
(VERNON), 401.
Secondary Réntgen radiation from air and ethyl bromide (CROWTHER), 101.
Secondary Réntgen Rays from Metallic Salts (GuAsson), 437.
Sez, W. J., Further study of the Products of Chlorination of a-Picoline, 546.
Sex in rabbits, Alleged influence of lecithin upon the determination of
(PUNNETT), 92.
604. Index.
SHARPE, H. J., On the Reflection of Sound at a Paraboloid, 190.
Suaw, T. K., Elected Fellow 1909, November 22, 591.
Shore-crab, Changes in the Common, caused by Sacculina (Ports), 96.
Sinciair, F. G., Note on the abnormal pair of appendages in Lithobius, 235.
Sodium, Double fluorides of (WILKs), 76.
Sodium, The radiation of various spectral lines of (PURVIS), 45.
Solutions, Some general Properties of Mixed (VEGARD), 275.
Sound, Reflection of, at a Paraboloid (SHARPE), 190.
SouTHERNS, L., Experimental Investigation as to Dependence of the Weight
of a Body on its state of Electrification, 352.
Stratton, F. J. M. and Compton, R. H., On Accident in Heredity, with
special reference to Right- and Left-Handedness, 507.
STRICKLAND, OC. and SWELLENGREBEL, N. H., The development of Trypanosoma
lewist in the Rat Flea (Ceratophyllus fasciatus), 531.
Substances, The mode of action of specific (Dixon and HamIt1), 54.
Summable functions, On a property of (Dixon), 210.
Swaln, H. T., Elected Associate 1910, May 23, 595.
SWELLENGREBEL, N. H. and StRICKLAND, C., The development of Trypanosoma
lewist in the Rat Flea (Ceratophyllus fasciatus), 531.
Taytor, G. I., Interference fringes with feeble light, 114.
Tetramethylpicene, Absorption spectra of solid (PURVIS and HoMER), 82.
Therapeutic Inoculation for Generalised Bacterial Infections (Noon), 24.
Thio-oxalate, A coloured (JONES), 94.
Tuopay, D., Elected Fellow 1910, February 7, 592.
Tuomas, H. H., Elected Fellow 1910, February 7, 592.
—— Ona specimen of the cone Calamostachys binneyana (Carr.), 226.
— On the assimilating tissues of some Coal Measure Plants, 418.
Tomson, J. J., On the Carriers of the Positive Charges of Electricity emitted
by hot wires, 64.
—— On the Electric Theory of Gravitation, 65.
— On the Distribution of Electric Force along the Striated Discharge, 70.
— On the theory of the motion of charged Ions through a Gas, 375.
— On the Scattering of rapidly moving Electrified Particles, 465.
—— On the phosphorescence observed on the glass of vacuum tubes when
the pressure is not very low, 482.
Toxaemia, The action of specific substances in (Dixon and HARvEy), 54.
Trichloromesitylene, Absorption spectra of (PURVIS), 89.
Trypanosoma lewist, Transmission of, by fleas and lice (NUTTALL), 53.
Trypanosoma lewisi in the Rat Flea, The development of (STRICKLAND and
SWELLENGREBEL), 531.
Tubercle Bacilli from some Old Tuberculous Lesions in Man, The Absence of
Living (CoBBETT), 536.
Tuberculosis, The Relationship between Human and Bovine (WooDHEAD), 40.
TURNBULL, H. W., The irreducible concomitants of two. quadratics in 2
variables, 296. See Transactions XXI.
Indec. 605
Turner, L. B., The stresses in a thick hollow cylinder subjected to internal
pressure, 591. See Transactions XXI.
Urethane, Action of (RUHEMANN and PRIESTLEY), 181.
Uric acid in the dog, The fate of (AcKRoyD), 547.
Uric acid derivatives, Formation of (FENTON and WILKs), 547.
Vecarp, L., On the Free Pressure in Osmosis, 13.
—— An experiment on ionisation with y-rays, 78.
—— On some general Properties of Mixed Solutions, 275.
Velocities of diffusion in aqueous solutions of rubidium and caesium chlorides
(Minzs and HIx1), 381, 387.
Vernon, R. D., On the occurrence of Schizoneura paradoxa, Schimper and
Mougeot, in the Bunter of Nottingham, 401.
Watson, G. N., Elected Fellow 1908, October 26, 292.
—— The continuations of functions defined by generalised hypergeometric
series, 591. See Transactions XxXI.
Weight of a Body on its state of Electrification, Dependence of the
(SOUTHERNS), 352.
Wetuiscu, E. M., Elected Fellow 1910, March 14, 594.
— The Laws of Mobility and Diffusion of the lons formed in Gaseous
Media, 1.
—— An Electric Detector for Electromagnetic Waves, 337.
WHELDALE, M., On the nature of anthocyanin, 137.
Wuippineton, R., Note on the electrical behaviour of fluorescing iodine
vapour, 189.
—— Some fatigue effects of the cathode in a discharge tube, 183.
—— Preliminary note on the properties of easily absorbed Roéntgen Radia-
tion, 574.
Witks, W. A. R., Note on some double fluorides of sodium, 76.
—— The Absorption of Bromine by Lime, 526,
Wiuks, W. A. R. and Fenton, H. J. H., Formation of uric acid derivatives,
547.
Wits, L. J., Elected Fellow 1910, March 14, 594.
—— Notes on the genus Schizoneura, Schimper and Mougeot, 406.
WoopueaD, G. Sims, The Relationship between Human and Bovine Tuber-
culosis, 40.
—— The results of Sterilisation Experiments on the Cambridge Water, 559.
Youne, W. H., On Monotone Sequences of Continuous Functions, 292. See
Transactions XX1.
— On Uniform Oscillation, 295. See Transactions xxt.
—— On the Change of Order of Integration in an improper repeated Integral,
593. See Transactions xXxI.
Zygopterideae and Osmundaceae, The relation between the fossil (GorDoN),
398.
Cambridge :
PRINTED BY JOHN CLAY, M.A.
AT THE UNIVERSITY PRESS.
CONTENTS. _
On the Mobilities of the Ions produced in Air by Ultra- Violet Light. By -
A. Li. Hueues. (Communicated by Professor Sir J. J. TECH
~ (Four figs. in:-Text) . ‘
On a Dissymmetry im the Bnassien of the Cathode Par oles “iil are
produced by Homogeneous Rontgen Radiations. By R. T. Brarry. «
saat ~ (Communicated by Professor Sir J. J. THomson.) (One fig. in Text)
On Right- and Left- -Handedness in Barley. _ R. H, Compton. (One
fig. in Text)
On Accident in Pobedeis Buk roid popercnes s Right- cnr a
-\ Handedness. By F. J. M. STRATTON and R. H. Compron .
Discontinuities in Light Emission. 11. By Norman CAMPBELL «> sia
The Absorption of Bromine by Lime. By W. Aw R. “Wings, (Com-
municated by Dr Fenton) eee
Note .on the Reduction of ee Chloride By I H. 0. Jowns and
J. K.-Marrazws
The development of Trypanosoma oe mM tie Rat Flea (Ceratophyllus
fasciatus). By C. Srricknanp and Dr N. H. SWELLENGREBEL.
(Communicated by Professor NurraLn). .
- The Development of Gnomonia erythrostoma, the Cause “of Cherry "ay “Leaf
Scorch Disease. By F. T. Brooxs.
The Absence of Living Tubercle Bacilli from some Ole Tuber culous
Lesions in Man. By Dr Lovis Coppetr
‘PAGE oe
483 Be
Noieon the Radium-content of the Waters of the Cam, ‘Canbpiee Top :
Water and some Varieties of Charcoal. By JoHn: See (von
~ municated by Professor Sir J. J. Taomson) é
The Resolution of Externally Compensated Bases into ieee Optically
active components.. By Professor PorE and J. READ -, :
The Resolution of Drhydr. opapaverine, By Se PoPE and C,. s.
GIBSON
_ Further study of the Dion of Cilorinution - aPidiione By De Sih
Formation of uric acid derivatives. By Dr Fenton and W. A. R. WILKS:
The fate of uric acid in the dog. By Hanoy AckRoyn. (Ceprugiiedy
by Mr W. E. Dixon)
The Adsorption of Acids by Ui aot enies ‘By F. ROBINSON, Coes
municated by Dr FENTON) .. . A
The results of Sterilisation Expervments on the Cambridge Water. iY,
G. Sms WoopHEap 5 . sa
Preliminary note on the propertres 5A odistly absorbed Réntgen Radeon
By. R. Wuippineron. - (Communicated by. Protester Sir J. J.
THomson.) (One fig. indlext)
Further notes on the procession of Cnethocampa pinivora. ‘by ae EL
Brinprey. (Plates XIII, XIV) - A
Proceedings at the Meetings hele eae the San 1909-1910 : a
Index to Vol. XV.
iy
al Magy eadien
BLY
)
Nuh
Wh
A i
‘ Pan eric
seedy Wedd ed LM Vet
udeetton he
gave
tele Mew
We AleKele ve Shell oak
ane
ai bates bee ME
Widen pee teege f
Wiebe we:
Si veeavuns ange seh gist iM Ue tee AS
Pee eal valet ake Sait oyetabts WALI Sie dt dvci inf ahh) aA. Boedge ood
Ho ese uataltte@ arses icabhinp tart nid oy Benelle wy FEE ieaicyy
Se Nala ut aineseniescmbben sci p ip Bake wea Gey Nee 9
Fe sactueas NARS Tee Bah EA. et Hlette ODH Sh Meth
He eee ceehebrhrytuaidarde nem cf ath Bo) bre atthe Bin Mee ff
eee rasaed eth Bey acti eybets Fm) itp (Mobs Eada Bhs Bede tage gay 1h
MU Ae mefiepeh ascites thee mie tieeyy itn
ewer usa yea oat wan mie |
Nabe a ais Baap cab ANNsi by ate Dv oa Rieck eee Le A yeh ae
ae Meat egedath ig bem Wesh deen ham Gell ele gh wees We Mlle potion se teody Meth
Hess Webaien ba tATHPAIe een Dekeb es doen ce tbe pews poe vious
pence pins CA Mrem gy: Morwaliliyterisle ing Gt Nellged HOB ah at a atrenrna
aA ei ies ee ahaa ae ite bie et
hee TYamen ca cMiem cies) {ibs We gibaly AT eure] eR (SMa been Hate we
MUNA elter eats one oUMUE RY CELL 4 Aa aly was
a aesioaaper asia (eek ( Blehesens
Pons emer The ee a
, » attest
ite RE WER ied Si ood fie Abate aesy " bh) hy
Pua Aided kebes whoeey A
HM UNIS Poy eee i , ’
c at ry y ao +}
VALERA ms Arig sy Gee sau h 4
ip ehabyda be Hasta eps eaney § Orie a's ar
gihst CHAD AGERE TELE ! ‘ p
bad salty STE ee ar é i PY
Rit at Witt Abehiea AugtiSdL Aitasd ade ERAN) AIM Messy
SOR DL (eon biti ‘ a sted Part
eUPund eye Ui SSE RES ean ha OIE \
i mV ETAT HATS sd WRAL Men eiiehay cl etd
. ern Hise de slat de kee WAR images at
‘ EC PEN ATED TAT Eee LUE LEN ae Ree aebsk
Wauen ye OC Weah a sAcedd ede dg ee MENSA Hla ede SEs (ge died HOE SP
hs ewe LEA p) AIS 8 a ALM AIN Ub ‘ rye yest
edbeh he Db hc gcaem ach DAS OLbrA EAE said tah bedreb ely ‘4
Parity yerertcny ty bite tn ir dete (eens eri i i
Fey r we Ore ag tl ie ir eek WE Rt Heras recay ae ted QM b j
eae yi "
Wiha Gabraebire
bey dy hw bweg
v i
oe Vive e Ay
” teen wy
WHILE HD
pani) Pk ne
Ay oon ra cee ee
y
Wee
Wed
Vorue
a
all
'
rere
SMITHSONIAN INSTITUTION LIBRARIES
__ 3 9088 01303 3444
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11